Washington, D.C., was planned around a large right triangle, with the White House at the triangle's northern vertex and the U.S. Capitol at its eastern vertex, linked by Pennsylvania Avenue (as the hypotenuse).
The White House stands at one vertex of a large right triangle around which the city of Washington was built.
A 1793 survey established the location of the triangle's 90° vertex, and Thomas Jefferson, when he was Secretary of State, had a wooden post installed to mark the spot. This post was replaced in 1804 by a more substantial marker, which came to be known as the Jefferson Pier.
A granite marker now fills in for the original Jefferson Pier, which stood at the southwest corner of the right triangle defining the city of Washington. The lines on top of the stone represent the north-south (longitudinal) and east-west (latitudinal) directions.
Pierre L'Enfant's original design for the city had called for an equestrian statue of George Washington at the triangle's southwest corner, but it was never commissioned. A later design for the memorial featured a massive obelisk, but the ground was too unstable for it to be located at the intended spot. Instead, construction of the Washington Monument began at a site a short distance to the south and east of the Jefferson Pier.
The U.S. Capitol (left) stands due east of the Jefferson Pier, which is located a short distance to the north and west of the Washington Monument (right).
A memorial marker has now replaced the original Jefferson Pier. The White House is due north of the marker, and the Jefferson Memorial, completed in 1943, is due south.
The view southward from the Jefferson Pier to the Jefferson Memorial.
The Jefferson Memorial, Jefferson Pier, and White House all lie on what was once considered a potential prime meridian of the United States.
An equestrian statue of Andrew Jackson stands on the meridian north of the White House.
See "American Meridian" for information on the official U.S. prime meridian, established in 1850.
Photos by I. Peterson