If it had n’t been for the Mexican Cession of 1848,muchof the southwesterly United States — California , Arizona , New Mexico , and parts of Utah , Nevada , and Colorado — would still belong to Mexico . But you probably already knew that , thanks to your U.S. account moral in elementary school .
What does n’t typically appear in history books , however , is the township the United Statesreturnedto Mexico . And it was n’t ceded centuries ago — this happen in the 1970s .
The Rio Grande , as most people know , is the physical perimeter between Mexico and the United States , and has beensince 1845 . In 1906 , the Rio Grande Land and Irrigation Company feared that a new south - work curve in the river would result in implosion therapy and property damage , sothey illicitly diverteda portion of it . But solving that problem make a novel one:413 acres of U.S. landwere now all of a sudden locate south of the river . Although it was decided that this small parcel of Din Land , known as the Horcón Tract , would legally remain part of Texas , it wasadministered by Mexico .
In 1929 , the city of Rio Rico was form on the tract to take vantage of the boundary disarray . Though Prohibition was in full swing in the U.S. , visitors to the little town could imbibe and risk freely because the legal power was rather unsettled .
The boundary remained equivocal until 1967 , when James Hill , Jr. , a geography professor at Arizona State , fare across the issue while examine old geologic survey map . The United States Boundary Commission and the State Departmentbecame concerned , and in November 1970 , the U.S. officially cede the pamphlet of land to Mexico .
Two years later , Homero Cantu Trevino of Rio Ricofiled suitto prevent the U.S. from comport him from Texas to Mexico . Trevino argued that because he was born in Rio Rico in 1935 , he was legally a citizen of the U.S. An appeals lawcourt finally harmonize with him , and it was ruled [ PDF ] that all occupant born in the city before 1972 could retain U.S. citizenship , which resulted in a vast decrease in Rio Rico ’s population as residentsmovedelsewhere in the United States .
It ’s not the first time something like this has happened , by the direction . The Rio Grande hasshiftedquite a bite in 1852 , often due to flooding . By 1873 , the river had displace , changing 700 acres of Mexican land concern to as “ Chamizal ” into U.S. territory . The conflict over who owned the land increased tension between the U.S. and Mexico for a century . In fact , when President William Howard Taftmetwith Mexican president Porfirio Diaz in the then - electroneutral Chamizal to discuss the issue , they were very nearly assassinated — a security detail disarmed a human with a concealed shooting iron just infantry away from the leaders .
finally , in 1963 , the U.S. announceda border agreementthat would return most of Chamizal back to Mexico . The two country also agreed to jointly finance the construction of a trench that would keep the river on a situated path — and hopefully avoid inciting border disputes in the future tense .
