Jefferson Pier, Jefferson Stone, or the Jefferson Pier Stone, in Washington, D.C., marks the second prime meridian of the United States[1] even though it was never officially recognized, either by presidential proclamation or by a resolution or act of Congress. The monument is a 2-foot-square (0.6 m), 2-foot-tall, granitic monolith with crossing longitudinal and latitudinal lines engraved on its upper surface and with a defaced inscription engraved on its west surface.[2] It is on the National Mall almost due south of the center of the White House and the midline of 16th Street, NW, about due west of the center of the Capitol, almost due north of the center of the Jefferson Memorial and 390 ft (119 m) WNW of the center of the Washington Monument.[3][4][5]
According to a notation on Pierre (Peter) Charles L'Enfant's 1791 "Plan of the city intended for the permanent seat of the government of the United States . . .", Andrew Ellicott measured a prime meridian (longitude 0°0') through the future site of the U.S. Capitol.[6][7] (Shortly after L'Enfant prepared this plan, its subject received the name "City of Washington".) Secretary of State Thomas Jefferson supervised Ellicott's and L'Enfant's activities during the initial planning of the nation's capital city.
Jefferson hoped that the United States would become scientifically as well as politically independent from Europe. He therefore desired that the new nation's capital city should contain a new "first meridian". In 1804, Jefferson requested a survey of a meridian through the President's House (now named the White House) while living in the house when serving as President. It is not known why he requested a survey of a new meridian after he had previously directed a survey of a different one while serving as Secretary of State eleven years earlier. The meridian of the United States was changed to the center of the small dome of the old Naval Observatory in 1850, and finally replaced by the Greenwich Meridian as the legal prime meridian for both boundaries and navigation in 1912.
A prominent geometric feature of L'Enfant's plan was a large triangle formed by Pennsylvania Avenue, plus a line projected due south from the front doors of the President's House and a line projected due west from the center of the Capitol along which a 400 feet (122 m)-wide garden-lined "grand avenue" would travel for about 1 mile (1.6 km).[8] L'Enfant had originally selected the southwest corner of this right triangle as the location for an equestrian statue of George Washington, which was never built.[8] The new meridian line extending south from the center of the President's House was surveyed by Isaac Briggs using a transit and an equal altitude instrument. At the junction of the lines from the center of the President's House and the Capitol,[9] on October 15, 1804, Nicholas King, Surveyor of the City of Washington, erected "a small pier, covered by a flat free stone, on which the lines are drawn."[10] This established the Washington Meridian (sometimes termed the "16th Street Meridian"), now at a longitude 77°2'11.56" (NAD 83) west of the Royal Observatory, Greenwich. Another stone, the Capitol Stone, was erected where the north-south line from the President's House intersected a line extending west from the south end of the Capitol, and a third stone, the Meridian Stone, was erected on the north-south meridian two miles north on Peters Hill, now Meridian Hill. Neither of the two latter stones survives. Due to errors either when the Jefferson Pier was initially surveyed or when it was replaced, its center is now 2.23 ft (0.680 m) south of the Capitol's centerline.[11]
A pier is a massive pillar capable of supporting a great weight.[12] Most of the length of a surveying pier is buried vertically in the ground for stability. Free stone is fine grained stone soft enough to carve with a chisel, yet has no tendency to split in any preferential direction. Even though the marker was located on the south bank of Tiber Creek, which was later transformed into the Washington City Canal, and could have been used as a bollard to moor barges, that usage was not the reason it was called a "pier", because the surveyor who erected it had already used that term himself. The entire National Mall area west of the marker was once under water until West Potomac Park was created as a result of an engineering project under the direction of Peter Conover Hains from 1882 to 1891.[13]
The developers of the Washington Monument originally wanted it to be located at Jefferson Pier, but concerns about the bearing capacity of the soil prevented it. However, the marker served as a benchmark during the first phase of its construction. Without realizing its significance, the original marker was removed by the Corps of Engineers during 1872–1874 as part of a cleanup of the grounds around the unfinished stump of the Washington Monument, including grading the grounds, filling-in gullies, planting trees, constructing ornamental ponds and a broad carriage road around the stump.[14] On December 2, 1889 Colonel O. H. Ernst, Officer in Charge of Public Buildings and Grounds, erected a replacement marker above the recovered foundation of the original marker. An artifact sometimes confusing to and often overlooked by tourists, Jefferson Pier is maintained today by the National Park Service under its National Mall and Memorial Parks administrative unit. In 1890 a new monument, the Ellipse Meridian Stone, was placed by the Coast and Geodetic Survey in the center of the Ellipse in President's Park about 1506 feet (459 m) north of the Jefferson Pier in a more protected area.[15] Theodolite measurements showed the new Ellipse Meridian Stone stood 26 inches (0.66 m) from the longtitudinal line of the replacement Jefferson Stone, indicating one of the two markers was improperly located.
In 1920, Congress approved the placement of a new delineation stone on the Ellipse, the Zero Milestone, which is an itinerary marker from which official mileages from Washington would be determined.[16] The new marker, a gift of the Lee Highway Association, was for some reason placed one foot west of the original meridian line extending north-south from the center of the White House.
In 1943, the Jefferson Memorial was completed due south of the White House on the Washington Meridian.[5][17] As a result, the Jefferson Pier now stands on a line that passes between the centers of the "President's House" and the memorial dedicated to the president for whom the Pier is named.