View source for Washington meridians

{{for|the [[principal meridian]] in the U.S. state of Mississippi|Washington meridian (Mississippi)}}
The '''Washington meridians''' are four [[meridian (geography)|meridian]]s that were used as [[prime meridian]]s in the [[United States]] which pass through [[History of Washington, D.C.|Washington, D.C.]] The four that have been specified are:
# through the [[United States Capitol|Capitol]]
# through the [[White House]]
# through the [[old Naval Observatory]]
# through the [[United States Naval Observatory|new Naval Observatory]].

Their longitudes may be reported in three ways:
# relative to the local vertical used by astronomic observations
# relative to NAD 27 ([[North American Datum]] 1927), an [[Figure of the Earth|ellipsoid of revolution]] that is at mean sea level beneath triangulation station [[Meades Ranch Triangulation Station|Meades Ranch, Kansas]] (not Earth-centered);
# relative to NAD 83, an Earth-centered ellipsoid of revolution with dimensions chosen to best fit the undulating (±100 m) [[geoid]] (world-wide mean sea level).

NAD83 longitude of the Capitol is about 1.1 arc seconds less than its NAD27 longitude; astronomic longitude there is about 4 arc seconds less than NAD83.

==Capitol meridian==
[[Pierre Charles L'Enfant|Pierre (Peter) Charles L'Enfant]] specified the first [[meridian (geography)|meridian]] in his 1791 "''Plan of the city intended for the permanent seat of the government of the United States . . .''" (see: [[L'Enfant Plan]]).<ref>(1) [https://www.loc.gov/exhibits/treasures/tri001.html Pierre Charles L'Enfant's 1791 "''Plan of the city intended for the permanent seat of the government ....''"] ''in'' [https://www.loc.gov official website of the U.S. Library of Congress]. Retrieved 2008-08-13.</ref><ref name=facsimile>{{cite web|last=L'Enfant|first=Peter Charles|url=http://memory.loc.gov/cgi-bin/query/h?ammem/gmd:@field(NUMBER+@band(g3850+ct000512))|title=Plan of the city intended for the permanent seat of the government of t(he) United States : projected agreeable to the direction of the President of the United States, in pursuance of an act of Congress passed the sixteenth day of July, MDCCXC, "establishing the permanent seat on the bank of the Potowmac": (Washington, D.C.)|work=Photocopy of annotated facsimile created by U.S. Coast and Geodetic Survey, Washington, D.C. (1887)|publisher=[[Library of Congress]]|year=1791|access-date=2016-01-26}}</ref><ref>(1) [[Freedom Plaza]] in Northwest Washington contains an inlay of L'Enfant's Plan with a legend identifying the longitude of the Congress house as {{nowrap|0,0°}}.<br>(2) L'Enfant identified himself as "Peter Charles L'Enfant" during most of his life, while residing in the United States. He wrote this name on his [http://hdl.loc.gov/loc.gmd/g3850.ct000512 "Plan of the city intended for the permanent seat of the government of t(he) United States ...."] (Washington, D.C.) and on other legal documents. However, during the early 1900s, a French ambassador to the U.S., [[Jean Jules Jusserand]], poipularized the use of L'Enfant's birth name, "Pierre Charles L'Enfant". (See: Bowling, Kenneth R (2002). ''Peter Charles L'Enfant: vision, honor, and male friendship in the early American Republic.'' George Washington University, Washington, D.C.) The [[National Park Service]] identifies L'Enfant as "[https://web.archive.org/web/20070629094749/http://www.nps.gov/history/nr/travel/wash/text.htm#washington Major Peter Charles L'Enfant]" and as "[https://web.archive.org/web/20090114210737/http://www.nps.gov/history/nr/travel/presidents/washington_monument.html Major Pierre (Peter) Charles L'Enfant]" on its website. The [[United States Code]] states in {{USC|40|3309}}: "(a) In General.&mdash;The purposes of this chapter shall be carried out in the District of Columbia as nearly as may be practicable in harmony with the plan of Peter Charles L'Enfant."</ref> (Shortly after L'Enfant prepared this plan, its subject received the name "City of Washington".) His plan stated near its right side that the longitude of the Congress house, now called the Capitol, was {{nowrap|0,0°}}.<ref name=facsimile/>

L'Enfant's plan contained the following explanatory note:

<blockquote>In order to execute the above plan, [[Andrew Ellicott|Mr. Ellicott]] drew a true meridian line by celestial observation, which passes through the area intended for the Congress-House; this line he crossed by another line due east and west and which passes through the same area. These lines were accurately measured, and made the basis on which the whole plan was executed. He ran all the lines by a [[transit instrument]], and determined the [[Angle#Individual angles|acute angle]]s by actual measurement, and left nothing to the uncertainty of the compass.<ref name=facsimile/></blockquote>

The longitude of the center of the Capitol's dome (completed in 1863 during the [[American Civil War|Civil War]]) is now given by the [[National Geodetic Survey]] as {{nowrap|77°00′32.6″W (NAD 83)}}.

==White House meridian==
[[File:Jefferson Pier and Washington Monument.jpg|thumb|West side of Jefferson Pier in April 2011 with Washington Monument in background.]]
[[File:Zeropost-1923.jpg|thumb|Zero Milestone, 1923, looking north toward the White House.]]
L'Enfant planned Washington around a [[right triangle]], having its 90° vertex at an equestrian statue of [[George Washington]], its eastern vertex at the "Congress house" and its northern vertex at the President's House, now named the "White House".<ref>{{cite web|url=http://www.nps.gov/history/nr/twhp/wwwlps/lessons/62wash/62locate1.htm |title=Map 1: The L'Enfant Plan for Washington |publisher=National Park Service |access-date=2009-10-27 |url-status=dead |archive-url=https://web.archive.org/web/20090121111024/http://www.nps.gov/history/nr/twhp/wwwlps/lessons/62wash/62locate1.htm |archive-date=January 21, 2009 }}</ref> (This would place L'Enfant's statue {{convert|0.36|m|sp=us}} north of the latitude of the Capitol.)

The west side of L'Enfant's triangle forms a natural prime meridian passing through the center of the President's house. The following ten features on and near this "Washington Meridian" are listed from south to north:

* The center of the [[Jefferson Memorial]], completed on the meridian in 1943.<ref>Coordinates of center of Jefferson Memorial: {{coord|38.881379|-77.036546|format=dms|scale:2000|name=Center of Jefferson Memorial}}</ref>
* The ''[[Jefferson Pier]]''. In 1793 [[United States Secretary of State|Secretary of State]] [[Thomas Jefferson]] surveyed and marked with a wooden post the southwest vertex of L'Enfant's triangle, establishing the second Washington meridian, the one through the President's house. The wooden post was replaced by the ''[[Jefferson Pier]]'' in 1804, while Jefferson was [[President of the United States]]. After removal and replacement several times, it was permanently replaced in 1889 by a {{convert|2|ft|m|adj=mid|-square|1}}, 2-foot-tall, granite pier, now {{convert|390|ft|m|0}} WNW of the center of the [[Washington Monument]].<ref>Coordinates of Jefferson Pier: {{coord|38.889812|-77.036558|format=dms|scale:2000|name=Jefferson Pier}}</ref> NGS gives its longitude as {{nowrap|77°02′11.56258″W (NAD 83)}} {{as of|2002|lc=y}} (likely error less than a centimeter). Azimuth to the Capitol is 89.98 degrees, a discrepancy of just under a meter.
* The [[German-American Friendship Garden]] on the Washington Monument grounds, dedicated on November 15, 1988.<ref>Coordinates of German-American Friendship Garden: {{coord|38.89187|-77.036550|format=dms|scale:2000|name=German-American Friendship Garden}}</ref>
* The [[Meridian Stone]]. Set In 1890 at the center of the [[President's Park#The Ellipse|Ellipse]], it was intended to be on the same meridian.<ref>Coordinates of Meridian Stone: {{coord|38.893943|-77.036548|format=dms|scale:2000|name=Meridian Stone}}</ref> It is an {{convert|18|in|cm|adj=mid|-square|0}} granite post set flush with the ground. NGS gives its longitude as {{nowrap|77°02′11.55880″W (NAD 83)}} {{as of|2002|lc=y}} (likely error less than a centimeter).
* The [[Zero Milestone]]. Set in 1923 on the north side of the Ellipse, it was intended to be on the same meridian and to be the zero mileage point for all United States roads (but never was).<ref>Coordinates of Zero Milestone: {{coord|38.895117|-77.036561|format=dms|scale:2000|name=Zero Milestone}}</ref> It is a granite pillar about {{convert|18|in|cm|0}} square and about {{convert|3.5|ft|m|1}} tall. NGS gives its longitude as {{nowrap|77°02′11.57375″W (NAD 83)}} {{as of|2002|lc=y}} (likely error less than two centimeters).
[[File:WashingtonMeridianMarker.jpg|right|thumb|Tablet facing 16th Street, NW, on west wall of Meridian Hill Park in 2006. The tablet states that a Washington Meridian marker stone was formerly located {{convert|52|ft|9|in|m|1}} west of the tablet.]]
* The center of the White House.<ref>Coordinates of center of the White House: {{coord|38.897680|-77.036558|format=dms|scale:2000|name=Center of White House}}</ref>
* [[Clark Mills (sculptor)|Clark Mills]]' equestrian statue of President [[Andrew Jackson]] in [[President's Park#Lafayette Park|Lafayette Park]], erected on the meridian in 1853 (see: [[Andrew Jackson (Mills)|''Andrew Jackson'' (Mills)]]).<ref>Coordinates of equestrian statue of Andrew Jackson in Lafayette Park: {{coord|38.899523|-77.036553|format=dms|scale:2000|name=Equestrian Statue of Andrew Jackson in Lafayette Park}}</ref>
* [[16th Street Northwest (Washington, D.C.)|16th Street Northwest]], which extends due north from the White House.<ref>Coordinates of south end of 16th Street NW: {{coord|38.900293|-77.036543|format=dms|scale:2000|name=South end of 16th Street NW}}</ref> The meridian is sometimes identified as the "16th Street Meridian" because of the location of this street.
* [[Meridian Hill Park#History|Meridian Hill]]. In 1804, a small freestone obelisk was placed at the crest of a hill, {{convert|1.5|mi|km|1}} north of the President's House. The marker, which no longer exists, was at the northern end of 16th Street, just north of [[Florida Avenue]], before 16th Street was extended northward about 1890,<ref>{{cite web|url=https://www.loc.gov/pictures/item/dc0826/|title= Sixteenth Street, Washington, District of Columbia, DC|work=Historic American Buildings Survey (HABS), Engineering Record, Landscapes Survey| page=5|id=HABS DC-717|archive-url=https://web.archive.org/web/20160127034842/https://www.loc.gov/pictures/item/dc0826/|archive-date=January 27, 2016|url-status=live}}</ref> covering it up. The park along the east side of 16th Street where the obelisk once stood still bears the name Meridian Hill Park.
[[File:DC Boundary Marker at SS traffic circle.jpg|thumb|Entrance marker stone near Silver Spring in traffic circle (Blair Circle) in December 2011]]
* [[Boundary Markers of the Original District of Columbia#District of Columbia entrance markers|District of Columbia entrance marker stone]] (approximately {{convert|66|ft|m}} east of this meridian) near [[Silver Spring, Maryland|Silver Spring]] in traffic circle (Blair Circle) at intersection of 16th Street Northwest, [[Eastern Avenue (Washington, D.C.)|Eastern Avenue Northwest]], N. Portal Drive Northwest and [[U.S. Route 29 in Maryland#Georgia Avenue and Colesville Road|Colesville Road]].<ref>Coordinates of District of Columbia entrance marker stone near [[Silver Spring, Maryland|Silver Spring]] in traffic circle at intersection of 16th Street Northwest, Eastern Avenue Northwest, N. Portal Drive Northwest and Colesville Road: {{coord|38.992322|-77.036326|format=dms|type:landmark|name=District of Columbia Boundary Marker Stone in traffic circle at intersection of 16th Street Northwest, Eastern Avenue Northwest and Colesville Road}}</ref>

==Old Naval Observatory meridian==
[[File:The American Meridian Line (38782358).jpg|thumb|200px|Meridian four blocks north of Old Naval Observatory, looking south in August 2005.<ref>Coordinates of "The American Meridian" line in sidewalk of H Street NW at 24th Street NW, in southeast corner of intersection: {{coord|38.8995|-77.051315|format=dms|scale:2000|name=American Meridian}}</ref>]]
The third meridian was defined on September 28, 1850, by [[United States Congress|Congress]]: "[T]he meridian of the observatory at Washington shall be adopted and used as the American meridian for all astronomical purposes and ... the meridian of Greenwich shall be adopted for all nautical purposes."<ref>[[s:Page:United States Statutes at Large Volume 9.djvu/541|'''9''' ''Statutes at Large'' 515]]</ref> The observatory decided that this meridian passed through the center of the original (small) dome atop the main building of the ''Old Naval Observatory'', now abandoned southwest of the corner of E and 23rd Streets in [[Foggy Bottom]] (north of the [[Lincoln Memorial]] and west of the White House). The observatory adopted {{nowrap|77°2′48.0″W}} for its meridian in the ''[[American Ephemeris and Nautical Almanac]]'' for the years 1855 to 1869 (as {{nowrap|5<sup>h</sup>8<sup>m</sup>11.2<sup>s</sup>)}}. In 1897, well after the observatory closed in 1892, the Coast and Geodetic Survey reported that its meridian was {{nowrap|77°3′2.3″}} west of Greenwich,<ref>'''3618''' ''Serial Set'' 254</ref> which was quoted for the next 50 years in the list of observatories in the ''Almanac'' (as {{nowrap|5<sup>h</sup>8<sup>m</sup>12.15<sup>s</sup>)}}. When referred to later datums, this meridian has been variously specified as {{nowrap|77°3′6.119″W}} or {{nowrap|77°3′6.276″W}} (both presumably NAD 27). If NAD27, the latter would be {{nowrap|77°3′5.194″W (NAD 83)}} which seems to be within a few meters of the actual longitude, at worst. This meridian was repealed by Congress on August 22, 1912, to allow the Greenwich meridian to become the legal prime meridian of the United States.

===Western state borders===
Many western states have borders that are meridians of "longitude west of Washington", that is, west of the legal 1850 meridian through the Old Naval Observatory. However, their present boundaries follow the subsequently surveyed boundary, even when inaccurately marked a few miles (kilometers) east or west of the meridian in the statute. Other western states have meridians relative to Greenwich ([[Alaska]], [[California]], [[Oklahoma]], [[Texas]]) or relative to a river or lake ([[Arkansas]], [[Louisiana]], [[Minnesota]], [[Missouri]], [[Oregon]], [[Washington (state)|Washington state]]).

The following meridians west of Washington are listed east to west, along with the appropriate boundary of the present state. The date of the meridian's definition is in parentheses (all in the 1860s). All states were territories of the same name when their meridians were specified except as noted. States without dates have boundaries dependent on the neighboring state with a date listed immediately above it.
[[File:Four Corners, NM, reconstructed monument in 2010.jpg|300px|thumb|[[Four Corners Monument]] 32° west of Washington Meridian, after 2010 reconstruction.<ref>Coordinates of Four Corners Monument: {{coord|36.998976|-109.045172|format=dms|region:US_type:landmark}}, {{convert|1807|ft|m}} east of 32°W at 31.9938°W.</ref>]]
{| class = wikitable
!Degree
!Boundary
|-
|rowspan=3| 17° || SW [[Arkansas]] (south of the [[Red River of the South|Red River]])
|-
| E [[Texas]] (between the Red and [[Sabine River (Texas-Louisiana)|Sabine]] Rivers)
|-
| NW [[Louisiana]] (north of the Sabine River)
|-
|rowspan=3| [[25th meridian west from Washington|25°]] || W [[Kansas]] (January 29, 1861) as a state
|-
| E [[Colorado]] (February 28, 1861), NE not dependent on Kansas
|-
| SW [[Nebraska]]
|-
|rowspan=5| [[27th meridian west from Washington|27°]] || E [[Montana]] (March 3, 1863) as Idaho Territory
|-
| E [[Wyoming]] (March 3, 1863) as Idaho Territory
|-
| NW Nebraska
|-
| W [[North Dakota]] as Dakota Territory
|-
| W [[South Dakota]] as Dakota Territory
|-
|rowspan=4| [[32nd meridian west from Washington|32°]] || W Colorado (February 28, 1861)
|-
|SE [[Utah]]
|-
|E [[Arizona]] (February 24, 1863)
|-
| W New Mexico
|-
|rowspan=4| [[34th meridian west from Washington|34°]] || SW Montana (May 26, 1864)
|-
|W Wyoming (July 25, 1868), SW not dependent on Montana
|-
|SE [[Idaho]]
|-
|NE Utah
|-
|rowspan=2| [[37th meridian west from Washington|37°]] || E [[Nevada]] (May 5, 1866) as a state (39° → 38° → 37°)
|-
|W Utah
|-
|rowspan=2| [[39th meridian west from Washington|39°]] || NW Montana (May 26, 1864)
|-
|NE Idaho
|-
|rowspan=1| [[43rd meridian west from Washington|43°]] || W [[Nevada]] (1864)<ref name="CA v. NV">{{cite court |litigants=California v. Nevada |vol=44 |reporter=U.S. |opinion=125 |court=[[Supreme Court of the United States]] |date=1980 |url=https://www.law.cornell.edu/supremecourt/text/447/125 |access-date=June 4, 2018 |quote=Nevada's Constitution stated that its boundary would proceed "in a North Westerly direction along [the oblique section of the] Eastern boundary line of the State of California to the forty third degree of Longitude West from Washington [and then] North along said forty third degree of West Longitude, and said Eastern boundary line of the State of California to the forty second degree of North Latitude. ..." Nev.Const., Art. XIV, § 1 (1864). Although it turns out that the 43d degree of longitude west from Washington does not exactly coincide with the 120th meridian west of Greenwich—which was the north-south reference in the California Constitution}}</ref>
|}

==New Naval Observatory meridian==
{{Unreferenced|section|date=September 2023}}
The fourth meridian was through the clock room of the new Naval Observatory, {{convert|2.3|mi|km|abbr=on}} northwest of the White House, at {{nowrap|77°3′56.7″W (1897)}} or {{nowrap|77°4′2.24″W (NAD 27)}} or {{nowrap|77°4′1.16″W (NAD 83)}}. The clock room is a small building at the exact center of the {{convert|1000|ft|m|abbr=on}} radius observatory grounds, whose northern entrance is at 34th Street and Massachusetts Avenue. It was used in the ''Almanac'' for the years 1898–1950 as the independent variable of time for a few tables (even though Washington's civil time since 1883 had been that of the standard time zone GMT−5 hours (75°W)).

==See also==
*[[Washington mean time]]
*[[International Meridian Conference]]

==Notes==
{{reflist}}

==References==
* {{cite book|last=Bedini|first=Silvio A.|title=The Jefferson Stone: Demarcation of the First Meridian of the United States|place=Frederick, MD|publisher=Professional Surveyors Publishing Co.|year=1999|author-link=Silvio Bedini}}
** {{cite journal|last=Toscano|first=Patrick|url=http://archives.profsurv.com/magazine/article.aspx?i=541|title=Book Review: Bedini, Silvio A. (1999), ''The Jefferson stone: Demarcation of the First Meridian of the United States''|journal=Professional Surveyor|place=Frederick, MD|date=January 2000|volume=20|issue=1|access-date=2010-07-16}}
** {{cite journal|last=Waff|first=Craig B.|bibcode=2001JHA....32..157W|title=''A Prime Meridian for the United States?'' Essay Review of Bedini, Silvio A. (1999), ''The Jefferson stone: Demarcation of the First Meridian of the United States''|journal=Journal for the History of Astronomy|volume=32, Part 2|issue=106|pages=157–159|issn=0021-8286|place=Cambridge, England|publisher=Sage journals]|date=May 2001|doi=10.1177/002182860103200209|s2cid=220268689|doi-access=free}} Note: Contains much information from book.
* {{cite journal | last1 = Pratt | first1 = Joseph Hyde | year = 1942 | title = American Prime Meridians | journal = Geographical Review | volume = 32 | issue = 2| pages = 233–244 | doi=10.2307/210272| jstor = 210272 | bibcode = 1942GeoRv..32..233P }}
* Van Zandt, Franklin K. ''Boundaries of the United States and the several states'', Geological Survey Professional Paper 909 (1976)
* ''American ephemeris and nautical almanac'' (Washington, DC: annual), preface and observatories

==External links==
{{GeoGroup|article=Washington meridian}}
* [https://web.archive.org/web/20140304025556/http://www.savethemall.org/mall/resource-hist02.html The 1791 L'Enfant plan and the Mall]
* [http://www.exploredc.org/index.php?id=3 Map of L'Enfant's Plan]
* [http://geodesy.noaa.gov/PUBS_LIB/WashMon.pdf Washington Monument GPS Project] including Jefferson Pier and Zero Milestone (1.29 MB)
* [http://www.labbey.com/Telescopes/Washington.html Washington Refractor] describing the condition of Old Naval Observatory in 1972.
* [http://www.ngs.noaa.gov/INFO/Washmon/info.htm Washington Monument GPS Height Modernization Project] listing coordinates of Jefferson Pier, Meridian Stone, and Zero Milestone (click on names for photos)

{{authority control}}
{{coord|38.895103|-77.0514428|dim:300000_region:region:US-DC_type:landmark|name=Old Naval Observatory|display=title}}

[[Category:Meridians (geography)]]
[[Category:Meridians and base lines of the United States]]
[[Category:Named meridians]]
[[Category:Prime meridians]]
[[Category:Geography of Washington, D.C.]]