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  5. Did You Know... Century-Old Obelisks Mark U.S.-Mexico Boundary Line?

Did You Know... Century-Old Obelisks Mark U.S.-Mexico Boundary Line?

Long before courses of concrete bollards, concertina wire and steel fences marked the boundary, those who patrolled our nation's borders relied upon the natural markers in the landscape and the border obelisks which dot the horizon. These obelisks, also known as Boundary Monuments, trace their roots to the Guadalupe Hidalgo Treaty of 1848 and the Gadsden Treaty of 1853, both of which redefined the international boundary between the U.S. and Mexico.

As settlements grew along the borderlands in the late 1800s, questions arose as to the exact location of the international boundary. Beginning in 1849, the first of several joint commissions were established by the U.S. and Mexico to survey, map, and demarcate the new boundaries which resulted under the Guadalupe Hidalgo and Gadsden Treaties.

Fifty-two boundary monuments were erected between 1849 and 1857 along the U.S - Mexico border. Of these monuments, most were simple stone mounds built without mortar, while seven were constructed with more substantial materials of marble or cast iron. Over time, the occasional destruction of these smaller stone monuments and the increasing population along the border led to the creation of the International Boundary Commission to resurvey and demarcate the western boundary in 1889. Starting in 1891 to 1894, IBC crews reconstructed old monuments and erected new ones, increasing the number of monuments from 52 to 258.

Today, one of the original fifty-two monuments rests a few hundred feet from the Pacific Ocean, nestled between Tijuana, Mexico, and San Diego at Border Field State Park. Built from a single block of polished marble, it was the first marker constructed along the border, which stretches nearly 2,000 miles between San Diego and Brownsville, Texas.

In 1971, First Lady Pat Nixon dedicated the land surrounding Monument No. 258 as "Friendship Park." Though it has long become a gathering spot for families separated by the border, all activity is not considered innocent. People have been caught in the area selling drugs, smuggling illegal immigrants and trading in false documents. This area of vulnerability is the responsibility of the Border Patrol's Imperial Beach Station. CBP personnel regularly patrol the grounds alongside California park officials and routinely operate a checkpoint to screen people leaving the park.

Have questions or comments? Do you have a story, photograph, video or artifact to share? Contact the CBP History Branch at

Last Modified: Dec 20, 2019