A change in the course of the Rio Grande in the 1860s in the vicinity of El Paso - Ciudad Juarez transferred less than one square mile from the south side of the river to the north side, yet it resulted in an international land dispute as tough and thorny as its namesake, the native Chamizo bush. It was the subject of international arbitration in 1911. This 100 year old "Chamizal" dispute was settled by treaty between the United States of America and the United Mexican States signed August 29, 1963, and proclaimed January 16, 1964. The president of the United States, Lyndon B. Johnson and the president of Mexico, Adolfo Lopez Mateos, met and commemorated the settlement in El Paso on September 25, 1964. The treaty provides for relocation of the channel of the Rio Grande as shown on the map, to effect a net transfer to Mexico of 437.18 acres, which is the area concluded to have been awarded to Mexico by the 1911 arbitration. The relocation also affects a transfer to the United States of 193.16 acres on Cordova Island, formerly an enclave of Mexican territory on the north side of the river channel, in exchange for an equal area downstream from the island. The relocation and appurtenant work will be performed by the International Boundary and Water Commission, United States and Mexico.