![Century Old Obelisks Mark U.S. Mexico Boundary Line Century Old Obelisks Mark U.S. Mexico Boundary Line](/sites/default/files/photo/monument6_monument6.jpg)
Old Monument No. 16, looking east, was built in the early 1850's to mark the U.S. - Mexico border. Courtesy National Archives (76-OM-1-144)
Old Monument No. 16, looking east, was built in the early 1850's to mark the U.S. - Mexico border. Courtesy National Archives (76-OM-1-144)