Washington Meridian - White House Meridian

White House Meridian

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". (This would place L'Enfant's statue 0.36 meter north of the latitude of the Capitol.)

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

1. The center of the Jefferson Memorial, completed on the meridian in 1943.
2. In 1793 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 2-foot-square (0.6 m), 2-foot-tall, granite pier, now 390 feet (119 m) WNW of the center of the Washington Monument. NGS gives its longitude as 77°02'11.56258"W (NAD 83) as of 2002 (likely error less than a centimeter). Azimuth to the Capitol is 89.98 degrees, a discrepancy of just under a meter.
3. In 1890 the Meridian Stone was set at the center of the Ellipse, intended to be on the same meridian. It is an 18-inch-square (46 cm) granite post set flush with the ground. NGS gives its longitude as 77°02'11.55880"W (NAD 83) as of 2002 (likely error less than a centimeter).
4. In 1923, the Zero Milestone was set on the north side of the Ellipse, intended to be on the same meridian and to be the zero mileage point for all United States roads (but never was). It is a granite pillar about 18 inches (46 cm) square and about 3.5 feet (1.1 m) tall. NGS gives its longitude as 77°02'11.57375"W (NAD 83) as of 2002 (likely error less than two centimeters).
5. The center of the White House.
6. Clark Mills' equestrian statue of President Andrew Jackson in Lafayette Park, erected on the meridian in 1853.
7. 16th Street Northwest, which extends due north from the White House. The meridian is sometimes identified as the "16th Street Meridian" because of the location of this street.
8. The following feature on this meridian no longer exists. It was a small freestone obelisk placed in 1804 on top of a hill 1.5 miles (2.4 km) north of the President's House, hence the name Meridian Hill. It was at the northern end of 16th Street, just north of Florida Avenue, before 16th Street was extended northward soon after 1900, covering it up. Now adjoining the east side of 16th Street where the obelisk once stood is Meridian Hill Park.
9. District of Columbia boundary marker stone (approximately 66 feet (20 m) east of this meridian) in traffic circle at intersection of 16th Street Northwest, Eastern Avenue Northwest and Colesville Road.