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 acute angles by actual measurement, and left nothing to the uncertainty of the compass. The longitude of the center of the Capitol's dome (completed in 1863 during the Civil War) is now given by the National Geodetic Survey as . 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 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. The Jefferson Pier. 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-tall, granite pier, now WNW of the center of the Washington Monument. NGS gives its longitude as (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. The Meridian Stone. Set In 1890 at the center of the Ellipse, it was intended to be on the same meridian. It is an granite post set flush with the ground. NGS gives its longitude as (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