 It is located on Monument Hill, an easily visible hill just south of the confluence of the Gila and Salt Rivers, in Avondale, Arizona, about 14 miles (23 kilometers) southwest of downtown Phoenix.The original marker was set in 1851 by John R. Bartlett.In 1934, the U.S. Coast and Geodetic Survey set triangulation station "INITIAL" approximately 15 feet from the initial point.