The most significant dispute remaining after the Chamizal Settlement in 1963 involved the location of the boundary in the area of Presidio, Texas, and Ojinaga, Chihuahua.

The American-Mexican Treaty Act of October 25, 1972 authorized participation by the United States IBWC section.

The relocated channel was aligned in the reach above Presidio-Ojinaga so as to transfer from north to the south side of the river 1,606.19 acres (650.00 ha) and in the second reach downstream from the two cities so as to transfer from the south to the north side a net area of 252 acres (102 ha).

This transfer was made in exchange for the transfer from the United States to Mexico of other land, including five parcels near Presidio, the Horcón Tract (after 1906 located south of the Rio Grande), and Beaver Island (La Isla de Morteritos), located in the river south of Roma, Texas, comprising 481.68 acres (194.93 ha) in total.

This provision transferred to Mexico the portion of the town of Río Rico, Tamaulipas, located within the Horcón Tract.