Río Rico, located on the Rio Grande in Hidalgo County, was separated from Texas by a "meander cut" in violation of the treaty between Mexico and the United States. The community was originally located north of the Rio Grande on a narrow finger of land surrounded by an S-shaped curve in the river. In July 1906, however, the American Rio Grande Land and Irrigation Company constructed a cutoff to force the river into a straighter channel. As a result, the 413 acres on which Río Rico is situated came to be located south of the river. The company was eventually taken to court and fined for the diversion of the river, but neither country resolved the issue of territorial rights. The United States never formally relinquished title to the land, since international law dictates that only natural changes of a river's course can transfer territory; over time, however, Río Rico came to be administered by the Mexican government. The issue of territorial rights drew notice once again in 1967, when James Hill, Jr., a geography professor at Arizona State University, rediscovered the shift while studying old geological survey maps. The United States Boundary Commission and the State Department investigated and confirmed Hill's findings, and in 1972 the United States officially ceded the tract of land to the Republic of Mexico. In 1972, however, a resident of Río Rico, Homero Cantú Treviño, filed suit to prevent the United States Immigration and Naturalization Service from deporting him from Texas to Mexico, arguing that he was an American citizen. In 1976 a judge ruled against him; the next year an appeals court ruled that because the 1906 cutoff was unauthorized, anyone born in Río Rico from 1906 to 1972 was entitled to United States citizenship. The Río Rican acreage is known in Mexico as the Horcón tract.