In 1848 the United States and Mexico signed the Treaty of Guadalupe Hidalgo which established the border between the two nations. Part of that border was the center of the Rio Bravo (Rio Grande del Norte). Under international law river boundaries change with normal erosion, but not with alosive action. From 1852 to 1868 a combination of erosion and alosive action changed the course of the river and caused a border dispute between the United States and Mexico that was Finally settled only in 1964.
     After nearly a century of dispute President John F. Kennedy announced that agreement had been reached on July 18, 1963.. This treaty accepted the recommendations of the International Boundary Commission that, in 1911, granted to Mexico all land south of the Rio Bravo in 1864. L. B. Johnson signed the Chamizal Treaty on December 21, 1963
     The United States of Mexico issued a stamp in 1964 commemorating the restoration of El Chamizal (the disputed area which takes its name from a desert plant) to Mexico, and to honor President John F. Kennedy. The background of the stamp shows a map outlining the Chamizal District and the new border.