The Journal of San Diego History
“La Mojonera” and the Marking of California’s
U.S.-Mexico Boundary Line, 1849-1851
Charles W. Hughes
Winner of the Marc Tarasuck AwardOn a bluff overlooking the “Arroyo de Tia Juana” several hundred feet up from
the shoreline of the Pacific Ocean, a boundary monument—La Mojonera—has
marked the start of the 1,952 mile line separating Mexico and the United States
for the last 156 years. Captain Edmund L. F. Hardcastle, of the U.S. Topographical
Engineers, and Ricardo Ramírez, a zoologist and botanist attached to the Mexican
Boundary Commission, dedicated it on July 14, 1851.^1 Today it is one of 276
monuments marking the boundary line running between El Paso, Texas, and the
Pacific coast.Charles W. Hughes is a local historian currently studying the history of California’s U.S. Mexico border.
He gratefully acknowledges the research assistance provided by the staffs of the Oceanside and San
Diego public libraries, San Diego State University Library, and the National Archives.John Russell Bartlett’s 1852 drawing of the Monument at the Initial Point on the Pacific from Bartlett’s Personal
Narrative of Exploration and Incidents in Texas, New Mexico, California, Sonora and Chihuahua (1854).
©SDHS, OP#17134.