View source for The Iron Bridge

{{Short description|Bridge across the River Severn in Shropshire, England}}
{{about|the bridge in Shropshire|the village named after it|Ironbridge|other uses|Iron Bridge (disambiguation)}}
{{Good article}}
{{Use British English|date=February 2023}}
{{Use dmy dates|date=April 2020}}
{{Infobox bridge
|bridge_name   = The Iron Bridge
|image         = [[File:Iron Bridge east side in February 2019 (cropped).jpg|300px]]
|caption       = The Iron Bridge (February 2019)
|owner         = [[Telford and Wrekin Council]]
|carries       = Pedestrian traffic
|crosses       = [[River Severn]]
|locale        = [[Ironbridge Gorge]], [[Coalbrookdale]] and [[Ironbridge, Shropshire|Ironbridge]]
|design        = [[cast iron|cast-iron]] [[truss arch bridge]]
|mainspan      = {{cvt|100|ft|6|in}}
|designer      = [[Thomas Farnolls Pritchard]]
|builder       = [[Abraham Darby III]] 
|fabricator    = [[Abraham Darby III]] 
|begin         = November 1777
|complete      = July 1779
|open          = 1 January 1781
|toll          = Free public access since 1950
|coordinates   = {{coord|52.62735|N|2.48550|W|name=The Iron Bridge|display=inline,title}}
| embedded = {{Infobox designation list
| embed = yes
| designation1 = Scheduled monument      
| designation1_offname = The Iron Bridge<ref name=he/>  
| designation1_date = {{Start date and age|1934|01|18|df=yes}}<ref name=he/>  
| designation1_number = 1015325<ref name=he/>  
| designation2         = UK Grade I
| designation2_offname = The Iron Bridge<ref name="G1"/>
| designation2_date    = {{Start date and age|1983|04|08|df=yes}}<ref name="G1"/>   
| designation2_number  = 1038659<ref name="G1">{{National Heritage List for England |desc=The Iron Bridge|num=1038659|access-date=3 April 2021}}</ref>
}}
}}

'''The Iron Bridge''' is a cast iron [[arch bridge]] that crosses the [[River Severn]] in [[Shropshire]], England. Opened in 1781, it was the first major bridge in the world to be made of [[cast iron]]. Its success inspired the widespread use of cast iron as a structural material, and today the bridge is celebrated as a symbol of the [[Industrial Revolution]].

The geography of the deep [[Ironbridge Gorge]], formed by glacial action during the [[Last Glacial Period|last ice age]], meant that there are industrially useful deposits of [[coal]], [[iron ore]], [[limestone]] and [[fire clay]] present near the surface where they are readily mined, but also that it was difficult to build a bridge across the river at this location. To cope with the instability of the banks and the need to maintain a navigable channel in the river, a single span iron bridge was proposed by [[Thomas Farnolls Pritchard]]. After initial uncertainty about the use of iron, construction took place over two years, with [[Abraham Darby III]] responsible for the ironwork. The bridge crosses the Ironbridge Gorge with a main span of {{cvt|100|ft|6|in}}, allowing sufficient clearance for boats to pass underneath.

In 1934 it was designated a [[scheduled monument]] and closed to vehicular traffic. [[Toll bridge|Tolls]] for pedestrians were collected until 1950, when the bridge was transferred into public ownership. After being in a poor state of repair for much of its life, extensive restoration works in the latter half of the 20th century have protected the bridge. The bridge, the adjacent settlement of [[Ironbridge]] and the Ironbridge Gorge form the [[UNESCO]] Ironbridge Gorge [[World Heritage Site]].

== History ==

===Background===

The [[Ironbridge Gorge]] was formed at the end of the [[Last Glacial Period|last ice age]] by the overflowing of [[Lake Lapworth]], which resulted in the exposure of useful deposits of resources such as [[coal]], [[iron ore]], [[fire clay]] and [[limestone]] near the surface where they were readily mined.<ref name="Wills">{{cite journal
  |last=Wills
  |first=L.J.
  |author-link=Leonard Johnston Wills
  |year=1924
  |title=The Development of the Severn Valley in the Neighbourhood of Iron-Bridge and Bridgnorth
  |journal=[[Quarterly Journal of the Geological Society|J. Geol. Soc.]]
  |volume=80
  |issue=1–4
  |pages=274–308
  |doi=10.1144/GSL.JGS.1924.080.01-04.15
  |s2cid=130464410
  |url=http://jgslegacy.lyellcollection.org/content/80/1-4/274.abstract
  |access-date=9 April 2020
  |archive-date=16 November 2016
  |archive-url=https://web.archive.org/web/20161116171906/http://jgslegacy.lyellcollection.org/content/80/1-4/274.abstract
  |url-status=dead
  |url-access=subscription
  }}</ref> With the river providing a means of transport, the local area was an important centre of the emerging [[Industrial Revolution]].<ref>{{cite web |url=https://www.telford.gov.uk/download/downloads/id/5626/igwhs_management_plan.pdf |title=The Ironbridge Gorge World Heritage Site Management Plan |date=February 2017 |publisher=[[Telford and Wrekin Council]] |access-date=9 April 2020}}</ref>

[[Abraham Darby I]] first smelted local iron ore with [[Coke (fuel)|coke]] made from [[Coalbrookdale]] coal in 1709, and in the coming decades [[Shropshire]] became a centre for industry due to the low price of fuel from local mines.{{sfnp|Cossons|Trinder|2002|p=3}} The [[River Severn]] was used as a key trading route, but it was also a barrier to travel around the deep Ironbridge Gorge, especially between the then important industrial parishes of [[Broseley]] and [[Madeley, Shropshire|Madeley]], the nearest bridge being at [[Buildwas]] {{convert|2|miles}} away.{{sfnp|Cossons|Trinder|2002|pp=3–4}}<ref name=eh>{{cite web |url=https://www.english-heritage.org.uk/daysout/properties/iron-bridge/history-and-research/ |archive-url=https://web.archive.org/web/20140407091855/http://www.english-heritage.org.uk/daysout/properties/iron-bridge/history-and-research/ |archive-date=7 April 2014 |title=History and Research: Iron Bridge |publisher=English Heritage |access-date=4 April 2014}}</ref> The Iron Bridge was therefore proposed to link the industrial town of Broseley with the smaller mining town of Madeley and the industrial centre of Coalbrookdale. The use of the river by boat traffic and the steep sides of the gorge meant that any bridge should ideally be of a single span, and sufficiently high to allow tall ships to pass underneath.<ref name=eh/><ref name=bros>{{cite web |url=http://www.broseley.org.uk/Archive/Broseley/Iron%20bridge.htm |title=John Wilkinson and the Iron Bridge |publisher=Broseley Local History Society |access-date=4 April 2014}}</ref> The steepness and instability of the banks was problematic for building a bridge, and there was no point where roads on opposite sides of the river converged.<ref name=p4-5>{{harvnb|Cossons|Trinder|2002|pp=4–5}}</ref>

The Iron Bridge was the first of its kind to be constructed, although not the first to be considered nor the first iron bridge of any kind. An iron bridge was partly constructed at [[Lyons]] in 1755, but was abandoned for reasons of cost,<ref>{{harvnb|Charlton|2002|p=11}}</ref> and a {{convert|22.2|m|ftin|adj=on|order=flip}} span [[wrought iron]] footbridge over an ornamental waterway was erected in [[Kirklees]], [[Yorkshire]], in 1769.<ref name=p9>{{harvnb|Cossons|Trinder|2002|p=9}}</ref><ref>{{cite news |url=https://www.halifaxcourier.co.uk/news/your-say/iron-bridges-close-to-home-1-1935179 |title=Iron bridges close to home |date=3 August 2009 |work=Halifax Courier |archive-url=https://web.archive.org/web/20181021024657/https://www.halifaxcourier.co.uk/news/your-say/iron-bridges-close-to-home-1-1935179 |archive-date=21 October 2018 |access-date=9 April 2020}}</ref>

===Proposal===

In 1773, architect [[Thomas Farnolls Pritchard]] wrote to his 'iron mad' friend and local [[ironmaster]], [[John Wilkinson (industrialist)|John Wilkinson]] of Broseley, to suggest building a bridge out of [[cast iron]].<ref name=ib1>{{cite web |title=Thomas Farnolls Pritchard |url=http://www.ironbridge.org.uk/collections/our-collections/engineering/the-iron-bridge/thomas-farnolls-pritchard/ |archive-url=https://web.archive.org/web/20150405032444/http://www.ironbridge.org.uk/collections/our-collections/engineering/the-iron-bridge/thomas-farnolls-pritchard  |archive-date=5 April 2015 |publisher=ironbridge.org.uk |access-date=4 April 2014}}</ref><ref>{{harvnb|Beggs-Humphreys|2013|p=26}}</ref> Although he specialised in the design of chimneypieces and other items of interior decoration, and in funerary monuments, he had also previously designed both wooden and stone bridges.<ref name=p10-11>{{harvnb|Cossons|Trinder|2002|pp=10–11}}</ref><ref name=dnb>{{Cite ODNB|id=37866|title=Pritchard, Thomas Farnolls}}</ref>

During the winter of 1773–74, local newspapers advertised a proposal to petition Parliament for leave to construct an iron bridge with a single {{convert|120|ft|adj=on}} span.{{sfnp|Cossons|Trinder|2002|p=19}} In 1775, a subscription raised funds of between £3,000 and £4,000 (equivalent to £{{Inflation|UK-GDP|3000|1773|2016|r=-3|fmt=c|cursign=£}} to £{{Inflation|UK-GDP|4000|1773|2016|r=-3|fmt=c|cursign=£}} in 2016), and [[Abraham Darby III]], the grandson of Abraham Darby I and an ironmaster working at Coalbrookdale, was appointed treasurer to the project.{{sfnp|Cossons|Trinder|2002|p=19}}

In March 1776, the '''{{visible anchor|Benthall Bridge, Severn Act 1776}}''' ([[16 Geo. 3]]. c. 17) giving authorisation to build a bridge received [[royal assent]]. It had been drafted by Thomas Addenbrooke, secretary of the trustees, and John Harries, a London barrister,{{efn-lr|Harries may have been related to the local Reverend Harries.{{sfnp|Cossons|Trinder|2002|p=23}}}} then presented to the [[House of Commons of Great Britain|House of Commons]] by [[Charles Baldwyn]], MP for [[Shropshire (UK Parliament constituency)|Shropshire]].{{sfnp|Cossons|Trinder|2002|p=23}} Abraham Darby III was commissioned to [[Casting|cast]] and build the bridge.<ref name=eh/><ref>{{cite web |url=http://www.ironbridge.org.uk/collections/the-iron-bridge/why-build-an-iron-bridge-in-coalbrookdale/ |archive-url=https://web.archive.org/web/20150215195838/http://www.ironbridge.org.uk/collections/the-iron-bridge/why-build-an-iron-bridge-in-coalbrookdale  |archive-date=15 February 2015 |title=Why build an Iron Bridge in Coalbrookdale? |publisher=Ironbridge Gorge Museum Trust |access-date=4 April 2014 }}</ref> In May 1776, the trustees withdrew Darby's commission, and instead advertised for plans for a single arch bridge to be built in "stone, brick or timber".<ref name=p15>{{harvnb|Cossons|Trinder|2002|p=15}}</ref> No satisfactory proposal was made, and the trustees agreed to proceed with Pritchard's design, but there was continued uncertainty about the use of iron, and conditions were set on the cost and duration of the construction.<ref name=p15/> In July 1777 the span of the bridge was decreased to {{convert|90|ft}}, and then increased again to {{convert|100|ft|6|in|1}}, possibly in order to accommodate a [[towpath]].<ref name=p16>{{harvnb|Cossons|Trinder|2002|p=16}}</ref>{{efn-lr|For a fuller description of the background of the construction of the bridge, see {{harvnb|Cossons|Trinder|2002|pp=9–18}}.}}

==Construction==

{{multiple image
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 | header    = Construction of the bridge
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 | image1    = Elias Martin Iron Bridge (cropped).jpg
 | alt1      = 
 | caption1  = Painting of the bridge by the Swedish painter [[Elias Martin]] in 1779. This is the only known painting during construction. 
 | image2    = Model of Iron Bridge, Blists Hill - geograph.org.uk - 1265172 (cropped).jpg
 | alt2      = 
 | caption2  = A modern-day reconstruction of how the Iron Bridge was assembled at [[Blists Hill Victorian Town]] in [[Telford]], [[Shropshire]]. 
 }}

The site, adjacent to where a ferry had run between Madeley and [[Benthall, Shropshire|Benthall]], was chosen for its high approaches on each side and the relative solidity of the ground.<ref name=eh/> The Benthall Bridge, Severn Act 1776 described how the bridge was to be built from a point in Benthall parish near the house of Samuel Barnett to a point on the opposite shore near the house of Thomas Crumpton.<ref name=p23>{{harvnb|Cossons|Trinder|2002|p=23}}</ref> Pritchard died on 21 December 1777 in his towerhouse at [[Eyton on Severn]], only a month after work had begun, having been ill for over a year.<ref name=ib1/><ref name=p17>{{harvnb|Cossons|Trinder|2002|p=17}}</ref>

The bridge is built from five sectional cast-iron ribs that give a span of {{convert|100|ft|6|in|1}}.<ref name=et/> The construction of the bridge used {{long ton|378|10}} of iron, and there are almost 1,700 individual components, the heaviest weighing {{long ton|5|5}}.<ref name=p24>{{harvnb|Cossons|Trinder|2002|p=24}}</ref> Components were cast individually to fit with each other, rather than being of standard sizes, with discrepancies of up to several centimetres between 'identical' components in different locations.<ref name=sean>{{cite web | title=Secrets of the past: How Ironbridge was built | publisher=sean.co.uk | url=http://www.sean.co.uk/a/science/ironbridge.shtm | access-date=13 April 2014}}</ref>

The masonry and [[abutment]]s were constructed between 1777 and 1778, and the ribs were lifted into place in the summer of 1779.<ref name=s4>{{harvnb|Smith|1979|p=4}}</ref><ref name=et>{{cite web |url=http://www.engineering-timelines.com/scripts/engineeringItem.asp?id=80 |title=The Iron Bridge |publisher=engineering-timelines.com |access-date=13 April 2014}}</ref> The bridge first spanned the river on 2 July 1779, and it was opened to traffic on 1 January 1781.<ref name=b1>{{cite web |url=https://www.bbc.co.uk/history/british/victorians/iron_bridge_01.shtml |title=The Iron Bridge – How was it Built? |publisher=BBC |access-date=14 April 2014 |last=de Haan |first=David |date=17 February 2011}}</ref><ref name=do>{{cite web |url=http://www.english-heritage.org.uk/daysout/properties/iron-bridge/ |title=The Iron Bridge |publisher=English Heritage |access-date=4 April 2014}}</ref>

In 1997, a watercolour by [[Elias Martin]] was discovered in a [[Stockholm]] museum, which showed the bridge under construction in 1779.<ref name=b1/> The painting shows a moveable wooden scaffold consisting of [[derrick]] poles standing in the river bed being used as a crane to position the half-ribs of the bridge, which had been taken to the site by boat from [[Madeley Wood Company|Darby's foundry]] {{convert|500|m}} downstream. Using the approach depicted in the painting, a half-size replica of the main section of the bridge was built in 2001 as part of the research for the [[BBC]]'s ''[[Timewatch]]'' programme, which was shown the following year.<ref name=b1/><ref>{{cite web |url=https://www.bbc.co.uk/shropshire/content/articles/2005/04/08/history_ironbridge_mystery_feature.shtml |title=Solved – The mystery of Ironbridge |publisher=BBC |access-date=10 June 2014 | archive-url=https://web.archive.org/web/20121025163545/http://www.bbc.co.uk/shropshire/content/articles/2005/04/08/history_ironbridge_mystery_feature.shtml |archive-date=25 October 2012}}</ref>

=== Design ===
[[File:Iron Bridge detail of north end from the east, February 2019.jpg|thumb|upright|Structural detail of the arches]] 
The bridge is to a carpenters' design typically used for wood structures, built from five sectional cast-iron ribs that give a span of {{convert|100|ft|6|in}}.<ref name=et/> The interlocking rings between the arches make this a [[truss arch bridge|truss arch]]. Exactly {{long ton|378|10}} of iron was used in the construction of the bridge, and there are almost 1,700 individual components, the heaviest weighing {{convert|5.5|lt|abbr=off}}.<ref name=et/><ref name=ap7>{{harvnb|Briggs|1979|p=7}}</ref> Components were cast individually to fit with each other, rather than being of standard sizes, with discrepancies of up to several centimetres between 'identical' components in different locations.<ref name=sean/>

[[File:Decorative Ironwork on The Iron Bridge.jpg|thumb|Central decorative railings]]
Decorative rings and [[ogee]]s between the structural ribs of the bridge suggest that the final design was Pritchard's, as the same elements appear in a [[gazebo]] he rebuilt.<ref name=s4/><ref>{{National Heritage List for England | num=1219113 | desc=Gazebo in garden of number 5 (not included) | access-date=4 April 2015}}</ref> A foreman at the foundry, Thomas Gregory, drew the detailed designs for the members, resulting in the use of carpentry jointing details such as [[mortise and tenon]] joints and [[Dovetail joint|dovetails]].<ref name=eh/><ref name=et/>{{sfnp|Tilly|2002|p=167}}

The two outer ribs are engraved with the words: "This bridge was cast at Coalbrook-Dale and erected in the year MDCCLXXIX" ([[Roman numerals]] for 1779).

Two supplemental arches, of similar cast iron construction, carry a towpath on the southern bank and also act as [[flood arch]]es.<ref name=do/> A stone arch with a brick [[Vault (architecture)|vault]] carries a small path on the northern (town side) bank.<ref name=he>{{NHLE |num=1015325 |desc=The Iron Bridge |access-date=9 April 2019}}</ref>

===Material===
{{further|Cast iron#Cast-iron bridges|Cast-iron architecture}}
The Iron Bridge is made of cast iron. This is immensely strong in compression, but performs less well than [[steel]] and wrought iron when subjected to [[Tension (physics)|tension]] or [[bending moment]]s, because of its brittleness and lower [[Ultimate tensile strength|tensile strength]].<ref>{{cite thesis |title=The History of Wrought and Cast Iron |url=https://trace.tennessee.edu/cgi/viewcontent.cgi?article=3676&context=utk_gradthes |type=Master's Thesis |last=Dyke |first=Shawn Van |publisher=University of Tennessee |date=2004}}</ref> Analysis of an arch and a strut from the Iron Bridge revealed the following [[Chemical element|elemental]] compositions:<ref name=tyle123/>

{|class="wikitable sortable plainrowheaders"
|-
!rowspan=2|Element!!colspan=2|Proportion
|-
! scope=col| Arch
! scope=col| Strut
|-
! scope=row| [[Carbon]]
||2.65%||3.25%
|-
! scope=row| [[Silicon]]
||1.22%||1.48%
|-
! scope=row| [[Manganese]]
||0.46%||1.05%
|-
! scope=row| [[Sulphur]]
||0.102%||0.037%
|-
! scope=row| [[Phosphorus]]
||0.54%||0.54%
|}

The presence of 0.1% sulphur in cast iron is at the upper limit of what is acceptable, but the presence of sufficient manganese leads to the formation of harmless [[Manganese(II) sulfide|manganese sulphide]].<ref name=tyle123>{{harvnb|Tylecote|1992|p=123}}</ref>{{efn-lr|For further information about the processing of the iron used in the bridge, see Tylecote, R. F. (1992). ''A History of Metallurgy'', Second Edition. London: Maney Publishing}}

[[Puddling (metallurgy)|Puddled wrought iron]] was a much better structural material than cast iron but not widely available until after 1800, eventually becoming the preferred material for bridges, rails, ships and buildings until new steel making processes such as the [[Bessemer process]] were developed in the late 19th century.<ref>{{harvnb|Misa|1995}}</ref>

===Cost===
Darby had agreed to construct the bridge with a budget of £3,250 (equivalent to £426,353 in 2023){{efn-lr|name=fn1|According to the Bank of England inflation calculator. Retrieved 29 March 2023}} and this was raised by subscribers to the project, mostly from Broseley. While the actual cost of the bridge is unknown, contemporary records suggest it was as high as £6,000 (£787,113 in 2023){{efn-lr|name=fn1}}, and Darby, who was already indebted from other ventures, agreed to cover the excess.<ref name=p29>{{harvnb|Cossons|Trinder|2002|p=29}}</ref> However, by the mid-1790s the bridge was highly profitable, and tolls were giving the shareholders an annual [[dividend]] of 8 per cent.<ref name=p30>{{harvnb|Cossons|Trinder|2002|p=30}}</ref>

==Later history==
{{multiple image
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 | header    = 
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 | footer_align = left
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 | total_width =400
 | image1    = Iron Bridge Telford 1970 - geograph.org.uk - 2276418.jpg
 | alt1      = Black bridge in 1970
 | caption1  = The Iron Bridge in 1970 
 | image2    = The Iron Bridge (Aerial).JPG
 | alt2      = An aerial photo of the bridge, showing the close proximity of the main road alongside the river and the many building dotted nearby.
 | caption2  = Aerial view of the Iron Bridge in 2008
 }}

The opening of the bridge resulted in changes in the pattern of settlement in the gorge, and roads around the bridge were improved in the years after its construction.<ref name=p31-33>{{harvnb|Cossons|Trinder|2002|pp=31–33}}</ref> The town of [[Ironbridge]], taking its name from the bridge, developed at the northern end.<ref name=p31-33/> The trustees, as well as local hotel keepers and coach operators, promoted interest in the bridge among members of high society.<ref name=p31-33/>

===Repairs===

In July 1783, a {{convert|35|yard|adj=on}} wall was built in order to prevent the north bank from slipping into the river.{{sfnp|Cossons|Trinder|2002|p=47}} Cracks were found in the stone land arch on the south side in December 1784, and the neighbouring abutment showed signs of movement.<ref name="et" /> The gorge is very prone to landslides, and over 20 are recorded in the [[British Geological Survey]]'s National Landslide Database in the area.<ref >{{cite web
  |url=http://www.bgs.ac.uk/research/engineeringGeology/shallowGeohazardsAndRisks/landslides/ironbridgeGorge.html
  |title=Landslides in the Ironbridge Gorge, Shropshire
  |publisher=[[British Geological Survey]]
  |access-date=14 April 2014
}}</ref> It was suspected that the sides of the gorge were moving towards the river, forcing the feet of the arch towards each other, and consequently repairs were carried out in 1784, 1791 and 1792.<ref name="et" />{{sfnp|Cossons|Trinder|2002|p=47}}

It was the only bridge on the River Severn to survive the flood of February 1795 undamaged, due to its strength and small profile against the floodwaters.{{sfnp|Petroski|1996|p=161}} The medieval bridge at Buildwas was replaced with a cast iron bridge by [[Thomas Telford]], which, by virtue of superior design, required half the quantity of iron despite a longer span of {{convert|39|m|order=flip}}.{{sfnp|Lay|1992|p=272 }}{{sfnp|Powell|2013|p=57}} The [[Buildwas Bridge]] survived until 1906.{{sfnp|Lay|1992|p=272 }} Contrary to a [[List of common misconceptions|common misconception]], Telford was not responsible for the construction of the bridge itself.<ref >{{Cite news
  |last=Burns |first=Mark |date=July 3, 2018
  |title=Telford is 50 years old: so is it still a new town?
  |url=https://www.bbc.com/news/uk-england-44685914
  |access-date=26 June 2024
  |work=[[BBC]]
}}</ref><ref >{{Cite web
  |title=7 Things You Didn't Know About the Iron Bridge
  |url=https://www.english-heritage.org.uk/visit/places/iron-bridge/7-things-you-didnt-know/
  |url-status=live
  |archive-url=https://web.archive.org/web/20240224161337/https://www.english-heritage.org.uk/visit/places/iron-bridge/7-things-you-didnt-know/
  |archive-date=24 February 2024
  |access-date=26 June 2024
  |website=[[English Heritage]]
}}</ref>

In 1800 the trustees commissioned repairs which lasted for several years, which involved the replacement of the stone land arches with wooden ones to relieve pressure on the main span.<ref name="et" />{{sfnp|Cossons|Trinder|2002|p=47}} A proposal to build a rigid support between the abutments to keep them apart was found to be impossible with the available technology, but was achieved during the later restoration of the bridge in the 1970s.{{sfnp|Cossons|Trinder|2002|p=48}} In 1812, its construction was described as "very bad" by [[Charles Hutton]], and he predicted that it would not last for long, "though not from any deficiency in the iron-work", but due to cracks that had appeared in the stonework.{{sfnp|Hutton|1812|p=146}} The timber arches were replaced with cast iron ones in December 1820, and further repairs were necessary throughout the remainder of the 19th century.<ref name="et" />{{sfnp|Cossons|Trinder|2002|p=50}}

Around 1870, “Sir B. Baker stated that it had required patching for ninety years, because the arch and the high side arches would not work together. Expansion and contraction broke the high arch and the connexions between the arches. When it broke they fished it.{{efn-lr|Spanning a crack by bolting a pair of 'fishplates' across it.}} Then the bolts sheared or the ironwork broke in a new place. He advised that there was nothing unsafe; it was perfectly strong and the stress in vital parts moderate. All that needed to be done was to fish the fractured ribs of the high arches, put oval holes in the fishes, and not screw up the bolts too tight."{{sfnp|Chisholm|1911|p=542}}

On 24 August 1902, a {{convert|30|ft|adj=on}} length of [[parapet]] collapsed into the river, and a section of deck plate weighing around {{cvt|5|Lcwt|kg}} fell from the bridge in July 1903.{{sfnp|Cossons|Trinder|2002|p=50}} The opening of a toll-free concrete bridge in 1909 caused concern among the trustees, but it continued to be used by vehicles and pedestrians.<ref >{{cite web
  |title=A Watching Brief at the Free Bridge, Jackfield, Shropshire
  |url=http://www.shropshirehistory.org.uk/html/resource/resource:20110221114543
  |format=PDF
  |website=shropshirehistory.org.uk
  |access-date=20 July 2014
  |archive-date=5 March 2016
  |archive-url=https://web.archive.org/web/20160305005342/http://www.shropshirehistory.org.uk/html/resource/resource:20110221114543
  |url-status=dead
  }}</ref>{{sfnp|Cossons|Trinder|2002|pp=50–51}}

===Closure to vehicles===

{{multiple image
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 | image1    = Iron Bridge Toll House, February 2019.jpg
 | alt1      = The brick tollhouse at the south end of the bridge
 | caption1  = Iron Bridge Tollhouse 
 | image2    = IronbridgeTolls.jpg
 | alt2      = Antique table of bridge tolls now displayed on the outside of the toll house. Tolls range from a halfpenny for a pedestrian to two shillings for a large coach
 | caption2  = The historic table of tolls
 | image3    = The Town of Ironbridge from the Former Toll House geograph-6173130-by-Fabian-Musto.jpg
 | alt3      = Pedestrians walking over a bridge with red-brown hand rails
 | caption3  = Pedestrians on the bridge in 2019
 }}

A 1923 report by engineering consultants [[Mott, Hay and Anderson]] suggested that other than the paintwork, the main span of the bridge was in good condition. It was suggested that the metal deck of the bridge was dangerously heavy, and that after removing the dead weight the bridge should be reopened to vehicles no heavier than 2&nbsp;tons and restricted to the centre of the roadway.<ref name=p51>{{harvnb|Cossons|Trinder|2002|p=51}}</ref> A weight limit of 4&nbsp;tons was imposed, but the housing boom of the 1930s meant that drivers distributing tiles produced at [[Jackfield]] were insistent that they should be allowed to use the bridge, so the trustees took the decision to close it to vehicular traffic with effect from 18 June 1934.<ref name=p51/> [[Toll bridge|Tolls]] for pedestrians were collected until 1950, when ownership of the bridge was transferred to [[Shropshire County Council]].<ref name=ap8>{{harvnb|Briggs|1979|pp=50–51}}</ref> The tolls collected only marginally covered the cost of collection, leaving no budget for conservation, and the bridge had not been cleaned or painted for many years.<ref name=p51/> Due to its poor condition, between the 1940s and 1970s a number of suggestions were made to scrap and replace the bridge, or move it to a different location. In 1956 the county council made a proposal to demolish the bridge and replace it with a new one, but this plan did not come to fruition.<ref name=bros/> The [[Ironbridge Gorge Museum Trust]] was set up in 1967 with the aim of protecting industrial heritage in the Ironbridge Gorge, and was able to secure funding from the council to carry out repairs.<ref name=bbcscrap>{{cite news |url=https://www.bbc.co.uk/news/uk-england-shropshire-15871626 |title= Iron Bridge 'may have been scrapped' |date=26 November 2011 |author=Emma Kasprzak |work=BBC News |access-date=28 March 2020}}</ref>

===Restoration===

{{multiple image
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 | image1    = Ironbridge bridge being repaired in 1974 - geograph.org.uk - 126337.jpg
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 | caption1  = The Iron Bridge being repaired in 1974 
 | image2    = Iron Bridge geograph-6748633-by-Sandy-Gerrard.jpg
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 | caption2  = The Iron Bridge being repainted in 1980
 }}

With funding from Shropshire County Council, the [[Historic Buildings Council for England]], and the nascent Ironbridge Gorge Museum Trust, a programme of repairs took place on the foundations of the bridge at a cost of £147,000 between 1972 and 1975.<ref name=bbcscrap/><ref>{{cite news |url=https://www.bbc.co.uk/news/uk-england-shropshire-19817664 |title=Ironbridge Gorge gets £12m government grant |work=BBC News |date=4 October 2012 |access-date=13 April 2014}}</ref> The consulting engineers [[Sandford, Fawcett, Wilton and Bell]] decided to place a [[Reinforced concrete|ferro-concrete]] [[inverted arch]] under the river to counter inward movement of the bridge abutments.<ref name=et/><ref name=p52>{{harvnb|Cossons|Trinder|2002|p=52}}</ref> The arch was built by the [[Tarmac Group|Tarmac Construction Company]], starting in the spring of 1973, but unusually high summer floods washed over the cofferdam, frustrating hopes that the work could be done in a single summer.<ref name=p53-54>{{harvnb|Cossons|Trinder|2002|pp=53–54}}</ref> Filling material was removed from the south abutment to reduce its weight, and the arch through it was reinforced with concrete.<ref name=p52-53>{{harvnb|Cossons|Trinder|2002|pp=52–53}}</ref> The road surface was replaced with a lighter [[asphalt concrete|tarmac]], the stone of the abutments was renewed and the toll-house was restored as an information centre.<ref name=p54>{{harvnb|Cossons|Trinder|2002|p=54}}</ref> In 1980, the structure was painted for the first time in the 20th century, and the work was complete for the bicentenary of the opening, which was celebrated on 1 January 1981.<ref name=p54-55>{{harvnb|Cossons|Trinder|2002|pp=54–55}}</ref>

{{multiple image
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 | image1    = Cropped in of The Iron Bridge in 2014.jpg 
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 | caption1  = {{legend|#9dbcd4|[[Blue-gray|blue-grey]] was the colour of the bridge before restoration ''(image taken 2014).''}} 
 | image2    = Iron Bridge east side in February 2019.jpg 
 | alt2      = 
 | caption2  = {{legend|#A52A2A|[[Shades of brown#Red-brown (web color "brown")|red-brown]] is the colour of the bridge since restoration ''(image taken 2019).''}}  
 }}

Between 1999 and 2000, the bridge was scaffolded to allow examination by [[English Heritage]]. The bridge was also repainted and minor repairs were carried out.<ref name=p55>{{harvnb|Cossons|Trinder|2002|p=55}}</ref> In January 2017 English Heritage announced a £1.2&nbsp;million restoration project on the Iron Bridge, starting in September 2017, the "biggest ever conservation project" undertaken by English Heritage.<ref>{{cite news|url=https://www.shropshirestar.com/news/2017/01/03/work-on-shropshires-iron-bridge-to-start-soon/|title=Work on Shropshire's Iron Bridge to start soon|date=3 January 2017|work= Shropshire Star|access-date=24 July 2017}}</ref> The cost was quoted in 2018 at £3.6&nbsp;million, with English Heritage describing it as "an ambitious conservation of its ribs and arches, its stonework and decking."<ref>{{cite magazine |title=Attention span |first=Paul |last=Bloomfield |magazine=English Heritage Members' Magazine |date=March 2018 |page=25}}</ref> The project was created after extensive surveys of the area revealed that the historic structure was under threat due to stresses in the ironwork dating from the original construction, ground movement over the centuries, and an earthquake in the 19th century. Apart from the structural restoration, the bridge was also reverted from blue-grey to its original red-brown colour after forensic analysis revealed this was how the bridge looked when it was first erected.<ref name="eh9">{{cite web|url=https://www.english-heritage.org.uk/about-us/search-news/iron-bridge-colour/ |archive-url=https://web.archive.org/web/20201211055830/https://www.english-heritage.org.uk/about-us/search-news/iron-bridge-colour/|archive-date=11 December 2020|title=English Heritage Experts Uncover Original Colour of the Iron Bridge|publisher=[[English Heritage]] |access-date=6 April 2021}}</ref><ref>{{cite news |last1=Growcott |first1=Mat|title=Iron Bridge true colour found to be red|url=https://www.shropshirestar.com/news/local-hubs/telford/ironbridge/2018/08/31/take-it-as-red-more-of-iconic-iron-bridge-paintwork-revealed-as-work-continues/|access-date=27 February 2020|work=Shropshire Star |date=31 August 2018}}</ref>

{{multiple image
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 | image1    = Bridge defect1.jpg
 | alt1      = Cracked to the joint on the blue-gray bridge
 | caption1  = Cracked mortice joint<br />''(image taken 2003)'' 
 | image2    = Ironbridge2.jpg
 | alt2      = Radial 'hourglass' supports of the bridge, cracked through the dovetails at their end
 | caption2  = Broken supports<br />''(image taken 2004)''
 }}

The project was partly funded through the use of crowdfunding in which £47,545 was raised.<ref>{{cite news |title=Project Iron Bridge: saving an industrial icon|url=https://www.crowdfunder.co.uk/project-iron-bridge|access-date=27 February 2020}}</ref> It also received a €1,000,000 donation from the Hermann [[Reemtsma]] Foundation, a German foundation which mainly promotes cultural and social projects in northern Germany. This would also be the foundation's first funding in the United Kingdom.<ref>{{cite news|title=Project Iron Bridge receives funding from German foundation|url=https://www.bbc.co.uk/news/uk-england-shropshire-41967772|access-date=27 February 2020|work=BBC News |date=13 November 2017}}</ref> Following the works the bridge was reopened on 6 December 2018.<ref>{{cite news |last1=Smith |first1=Rob|title=Iron Bridge reopens following restoration|url=https://www.shropshirestar.com/news/local-hubs/telford/ironbridge/2018/12/06/cast-iron-praise-as-iron-bridge-is-reopened/|access-date=27 February 2020|work=Shropshire Star |date=6 December 2018}}</ref>

===Recognition===

The bridge, the adjacent settlement of [[Ironbridge]] and the Ironbridge Gorge form the [[UNESCO]] Ironbridge Gorge [[World Heritage Site]], which was created in 1986.<ref name="UNESCO1"/> The bridge is a Grade I [[listed building]],<ref name="G1"/> and is owned by [[Telford and Wrekin Council]].<ref name=eh/>

In 1934 it was designated a [[scheduled monument]],<ref name=he/><ref name=et/> and in 1979, the bridge was recognised by the [[American Society of Civil Engineers]] as an [[List of Historic Civil Engineering Landmarks|International Civil Engineering Landmark]].<ref>{{cite web |url=https://www.asce.org/project/iron-bridge/ |archive-url=https://web.archive.org/web/20180629152943/http://www.asce.org/project/iron-bridge/ |url-status=dead |archive-date=29 June 2018 |title=Iron Bridge |publisher=American Society of Civil Engineers |access-date=9 April 2020 }}</ref>

In 2020 the conservation and restoration work on the bridge was honoured in the [[Europa Nostra#European Union Prize for Cultural Heritage/Europa Nostra Award|European Heritage Awards/Europa Nostra Awards]], which includes up to 30 of the most outstanding heritage projects from all parts of Europe within the [[European Union|EU]] and [[European Economic Area|EEA]].<ref>{{cite web |title=Winners |url=https://www.europeanheritageawards.eu/winners/ |website=europeanheritageawards.eu |access-date=4 April 2021 |archive-url=https://web.archive.org/web/20201030132044/https://www.europeanheritageawards.eu/winners/ |archive-date=30 October 2020}}</ref><ref>{{cite web|title=English Heritage's Iron Bridge project wins European Heritage Award / Europa Nostra Award|url=https://www.europanostra.org.uk/post/uk-project-iron-bridge-winner-of-european-heritage-awards---europa-nostra-award|website=europanostra.org.uk|access-date=4 April 2021|date=18 June 2020|archive-date=22 April 2021|archive-url=https://web.archive.org/web/20210422144442/https://www.europanostra.org.uk/post/uk-project-iron-bridge-winner-of-european-heritage-awards---europa-nostra-award|url-status=dead}}</ref>

==Influence on bridge design==
The bridge, as the first bridge of significant size built of metal, had "considerable influence on developments in the fields of technology and architecture".<ref name="UNESCO1">{{cite web |title=World Heritage List: Ironbridge Gorge |url=https://whc.unesco.org/en/list/371/ |publisher=UNESCO |access-date=10 December 2019}}</ref>
The successful use of cast iron in 1781 pioneered the choice of that material for many subsequent bridges, and cast iron arches of considerable span were constructed late in the 18th and early in the 19th century.{{sfnp|Chisholm|1911|p=542}}

* In 1786, the revolutionary author and polymath [[Thomas Paine]] had models built to demonstrate the use of cast iron for bridges, and promoted these to the [[French Academy of Sciences|Academy of Sciences]] at Paris, and to the [[Royal Society]] in England. He went on to have manufactured and erected "a complete rib of 90 feet span, and 5 feet of height from the chord line to the center of the arch", weighing three tons. This was followed by a complete bridge of five ribs and {{convert|210|feet}} span which he had erected in a [[Yorkshire Stingo|field in Paddington]], but without buttresses it was merely for display and was dismantled after a year.<ref name="TPNHA1">{{cite web |author1=Thomas Paine |title=The Construction of Iron Bridges: Letter to US Congress, dated June 1803 |url=http://thomaspaine.org/essays/other/the-construction-of-iron-bridges.html |website=Thomas Paine National Historical Association |access-date=17 December 2019}}</ref>
* In 1793–96, the [[Wearmouth Bridge (1796)|Wearmouth Bridge]] was built with a span of {{convert|235|feet}}, constructed from cast iron in the form of cast [[voussoir]]s, somewhat like the voussoirs of a masonry bridge.{{sfnp|Chisholm|1911|p=542}} The bridge used some of the iron from Paine's bridge, which had been returned to the foundry in [[Rotherham]].<ref>{{cite journal |last=Armytage |first=W. H. G. |title=Thomas Paine and the Walkers: An Early Episode in Anglo-American Co-operation |journal=Pennsylvania History: A Journal of Mid-Atlantic Studies |volume=18 |issue=1 |date=1951 |pages=16–30 |jstor=27769176}}</ref>
* In 1795, a large flood in the Severn swept away all the bridges in the vicinity, except the Iron Bridge, where the open structure allowed the floodwaters to pass through. [[Thomas Telford]] was Surveyor of Public Works in Shropshire at the time.<ref name="BBC1">{{cite web |title=Telford – The builder of Britain|url=https://www.bbc.co.uk/shropshire/content/articles/2005/04/09/great_salopians_telford_feature.shtml |publisher=BBC |access-date=18 December 2019}}</ref> His design for the replacement bridge at Buildwas incorporated a high arch like the Iron Bridge, but it had a span {{convert|30|feet}} wider and used less than half the amount of iron.<ref name="ET1">{{cite web |title=Buildwas Bridge, site of |url=http://www.engineering-timelines.com/scripts/engineeringItem.asp?id=1314 |website=engineering timelines |access-date=11 December 2019}}</ref> Telford went on to design a series of cast iron bridges, the oldest of which to survive is the [[Craigellachie Bridge]].<ref name="EB2019">{{cite encyclopedia |encyclopedia=Encyclopedia Britannica |title=Bridge Engineering|url=https://www.britannica.com/technology/bridge-engineering |access-date=9 April 2020|author=Hubert Shirley-Smith |author2=David P. Billington |author3=Philip N. Billington |date=20 February 2020}}</ref>
* In 1799, the [[Coalport Bridge]] was rebuilt after the flood as a single span with three cast iron ribs. This 1799 version was re-modelled in 1818 with two additional ribs, and survives to the present day.<ref name="Grace1">{{cite web |title=Coalport Bridge |url=https://www.gracesguide.co.uk/Coalport_Bridge |website=Grace's Guide |access-date=17 December 2019}}</ref>

{{Gallery
|File:Cast iron bridge over River Wear at Sunderland 1796.jpg |[[Wearmouth Bridge (1796)|Wearmouth Bridge]] (1793–96)
|File:Buildwas Bridge (Telford's bridge).jpg |[[Buildwas Bridge]] by [[Thomas Telford]] (1795–96)
|Image:Coalport br1.jpg|The [[Coalport Bridge]] (1818), incorporating three ribs from 1799 and an additional two in 1818 
|File:Bridge in hill.jpg|[[Craigellachie Bridge]] (1814) by Telford
}}

==Artistic depictions==

[[File:William Williams The Iron Bridge.jpg|thumb|The original red-brown colour of the bridge can be seen in [[William Williams (artist)|William Williams']] 1780 painting, which was commissioned by Abraham Darby III.<ref name="eh9"/>|alt=A painting of the bridge, from mid-river, in the picturesque style of the period. Smoking furnaces can be seen in the distance and a [[Severn trow]] is alongside the bridge. Two wealthy coaches are visible, as are a well-dressed party of sightseers in a small boat.]]

Over fifty painters and engravers came to the area around Coalbrookdale between 1750 and 1830 to witness and record the rise of industry and changing landscape.<ref name=s4/> One of the first artists to depict the bridge was [[William Williams (artist)|William Williams]], who was paid 10 [[Guinea (British coin)|guineas]] ({{Inflation|UK-GDP|10.5|1777|2016|fmt=eq|cursign=£}}) in October 1780 by Darby for a drawing of the bridge.<ref name=p33-34>{{harvnb|Cossons|Trinder|2002|pp=33–34}}</ref> An engraving by [[Michael Angelo Rooker]] proved popular, and a copy was purchased by [[Thomas Jefferson]] where it was displayed in the dining room of [[Monticello]].<ref name=p35-36>{{harvnb|Cossons|Trinder|2002|pp=35–36}}</ref>

In 1979, the [[Royal Academy of Arts]] held an exhibition entitled "A View from the Iron Bridge" to commemorate the bicentenary of the bridge.<ref>{{harvnb|Smith|1979}}</ref>

== See also ==
<!--{{div col|colwidth=18em}}-->
* [[List of crossings of the River Severn]]
* [[Listed buildings in The Gorge]]
<!--{{div col end}}-->

==Notes==
{{Notelist-lr}}

== References ==

=== Citations ===
{{Reflist}}

=== Sources ===
* {{cite book |title=Iron Bridge to Crystal Palace: Impact and Images of the Industrial Revolution |last=Briggs |first=Asa |year=1979 |isbn=978-0-500-01222-2 |url=https://archive.org/details/ironbridgetocrys0000brig |url-access=registration |publisher=Thames and Hudson in collaboration with the Ironbridge Gorge Museum Trust }}
* {{cite book|last=Beggs-Humphreys|first=Mary|title=The Industrial Revolution|url=https://books.google.com/books?id=dRf_AQAAQBAJ&pg=PA26|year=2013|publisher=Routledge|isbn=978-1-136-61331-9}}
* {{cite book |last=Charlton |first=Thomas. M. |author-link=Thomas Malcolm Charlton |title=A History of the Theory of Structures in the Nineteenth Century |url=https://books.google.com/books?id=g-R4d1ROpPoC |year=2002 |publisher=Cambridge University Press |isbn=978-0-521-52482-7 }}
* {{cite book 
  |url=https://books.google.com/books?id=p0YfAQAAIAAJ |title=The Iron Bridge: Symbol of the Industrial Revolution 
  |first1=Neil |last1=Cossons |author-link1=Neil Cossons
  |first2=Barrie Stuart |last2=Trinder 
  |publisher=Phillimore 
  |year=2002 
  |orig-date=1979
  |isbn=978-1-86077-230-6 
}}
* {{cite EB1911 |wstitle=Bridges/History 2 |display=Bridges}}
* {{cite book |url=https://books.google.com/books?id=IoY3AAAAMAAJ |title=Tracts on Mathematical and Philosophical Subjects, Comprising Among Numerous Important Articles, the Theory of Bridges, With Several Plans of Recent Improvement |volume=1 |year=1812 |first=Charles |last=Hutton }}
* {{cite book |last=Lay |first=M. G. |title=Ways of the World: A History of the World's Roads and of the Vehicles That Used Them |url=https://archive.org/details/waysofworldhisto00laym |url-access=registration |year=1992 |publisher=Rutgers University Press |isbn=978-0-8135-2691-1}}
* {{cite book|title= A Nation of Steel: The Making of Modern America 1965-1925|url= https://archive.org/details/nationofsteelmak00misa|url-access= registration|last=Misa|first= Thomas J.|year=1995 |publisher = Johns Hopkins University Press|location= Baltimore and London|isbn= 978-0-8018-6502-2 }}
* {{cite book |title=Invention by Design: How Engineers Get from Thought to Thing |url=https://archive.org/details/inventionbydesig00petr |url-access=registration |first=Henry |last=Petroski |year=1996 |publisher=Harvard University Press |isbn=978-0-674-46368-4 }}
* {{cite book |last=Powell |first=John |title=Ironbridge Gorge Through Time |url=https://books.google.com/books?id=UnCIAwAAQBAJ |year=2013 |publisher=Amberley Publishing |isbn=978-1-4456-2896-7}}
* {{cite book |title=A View from the Iron Bridge |url=https://books.google.com/books?id=EB7qAAAAMAAJ |last=Smith |first=Stuart |year=1979 |publisher=Ironbridge Gorge Museum Trust |isbn=0-903971-09-7 }}
* {{cite book |last=Tilly |first=Graham |title=Conservation of Bridges |url=https://books.google.com/books?id=H24s_x4qPm0C |year=2002 |publisher=CRC Press |isbn=978-0-419-25910-7}}
* {{cite book|title=A History of Metallurgy, Second Edition|last=Tylecote|first=Ronald. F. |author-link=Ronald F. Tylecote |year=1992|publisher=Maney Publishing, for the Institute of Materials |url=https://books.google.com/books?id=4ZdTAAAAMAAJ |location= London|isbn=978-0-901462-88-6}}

== External links ==
{{Commons category|The Iron Bridge}}
* [https://www.ironbridge.org.uk/explore/the-iron-bridge-tollhouse/ Iron Bridge & Tollhouse – Ironbridge Gorge Museums Trust]
* [https://www.english-heritage.org.uk/visit/places/iron-bridge The Iron Bridge on the English Heritage website]
* [https://www.bbc.co.uk/history/british/victorians/launch_vt_iron_bridge.shtml Virtual tour, from the BBC] ([[VRML]] [[Plug-in (computing)|plugin]] required, then use PgUp/PgDn to move between viewpoints)
* [http://nora.nerc.ac.uk/508100/1/CR08157N.pdf A geological assessment of the landslides in the Ironbridge Gorge, Shropshire (Report)] {{Webarchive|url=https://web.archive.org/web/20140906175458/http://nora.nerc.ac.uk/508100/1/CR08157N.pdf |date=6 September 2014 }}
* {{YouTube|id=tEft-mjcvY0|title=BBC One Show: Official Opening of the Iron Bridge}}
* {{Structurae|id=20000038|title=The Iron Bridge}}
{{Ironbridge Gorge Museums}}
{{River Severn}}

{{DEFAULTSORT:Iron Bridge, The}}
[[Category:Archaeological sites in Shropshire]]
[[Category:Bridges across the River Severn]]
[[Category:Bridges in Shropshire]]
[[Category:Cast-iron arch bridges in England]]
[[Category:English Heritage sites in Shropshire]]
[[Category:Grade I listed buildings in Shropshire]]
[[Category:Historic Civil Engineering Landmarks]]
[[Category:Industrial Revolution in England]]
[[Category:Telford and Wrekin]]
[[Category:Scheduled monuments in Shropshire]]
[[Category:Bridges completed in 1779]]
[[Category:Museums in Shropshire]]
[[Category:Ironbridge Gorge]]
[[Category:Technology museums in the United Kingdom]]
[[Category:Ironbridge Gorge Museum Trust]]
[[Category:Former toll bridges in England]]
[[Category:Grade I listed bridges]]
[[Category:1779 establishments in England]]
[[Category:Ironbridge]]
[[Category:Coalbrookdale]]