The Treaty of Guadalupe-Hidalgo, signed on February 2, 1848, brought an end to the U.S.-Mexico War and called for the establishment of a U.S.-Mexico Boundary Commission. The Commission was charged with demarcating the new international boundary. The monument atop what is now Monument Mesa marks the spot where they began this arduous task. Through to the end of the nineteenth century, the original boundary marker atop Monument Mesa became a tourist attraction, and thousands of visitors chipped chunks of marble from the monument as souvenirs of their visit.

 

In the 1890s a new commission was charged with charting a more precise location of the international boundary.  It did so by increasing the number of border monuments to 258, establishing a line-of-sight from one to the next. This commission worked from East to West, so when they finished working at the mesa overlooking the Pacific Ocean, they commissioned the creation of a new monument to replace the original boundary marker. Wanting to preserve the new monument in its permanent location, now identified as Monument 258, the commissioners ordered that a protective metal fence be built around it.

 

Sometime after World War II – there is no record of precisely when, U.S.  officials decided to mark the international boundary atop Monument Mesa with strands of barbed wire.  
 

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