Treaty of Guadalupe Hidalgo

The Treaty of Guadalupe Hidalgo, signed on February 2, 1848, in Querétaro, México, officially ended the Mexican-American War. This agreement set the border between the United States and Mexico, determined the political position of the inhabitants of the ceded territory, and addressed economic relations between Mexico and the United States.

According to the treaty, Mexico ceded 500,000 square miles to the United States in exchange for 15 million U.S. dollars. This included the territory of the current states of Arizona, California, Nevada, New Mexico, and Utah and parts of Colorado and Wyoming. Approximately 100,000 individuals were living under Mexican governance in the affected territories at the time the treaty was signed.

Under the treaty, Mexicans living in the ceded territories were permitted to remain in the United States and become U.S. citizens or to move across the new border to Mexico. Regardless of their ancestry, all Mexican-origin residents remaining in U.S. territories after one year would automatically be granted U.S. citizenship once their territory achieved statehood.

The newly formed states violated the terms of the treaty, however, by invoking their constitutional power to determine citizenship eligibility on a state-by-state basis. Some states limited citizenship to “free whites” and argued that Mexicans should be on equal footing with Native Americans, who were not afforded full citizenship rights. Those Mexicans of mestizo/a (Spanish and Native American) and Afro-mestizo/a descent were classified as Mexican Indians rather than whites and were therefore denied political rights. In addition to being denied suffrage, Mexican-origin people not recognized as white were prohibited from practicing law, marrying Anglo-American women, or running for political offices such as district judge.

Violations of the treaty extended beyond political rights. The original treaty honored Mexican land titles, but the U.S. Senate deleted this article when they ratified the treaty. Subsequently, the legitimacy of land titles could be proven only in U.S. courts. The bias of the land claims courts, requirements of evidence of ownership, high fees charged by lawyers, length of the legal proceedings, and prevalence of squatters forced many Mexicans to give up claim to land they had owned before the U.S. conquest.

Although the citizenship rights guaranteed by the treaty were often denied in practice, the treaty's existence prohibited the passage of legalized forms of discrimination that were aimed at other groups. As a result of the treaty, Mexican immigrants were exempted from the Naturalization Act of 1790 and permitted to apply for naturalization. In the 20th century, the Treaty of Guadalupe Hidalgo was used in the landmark Mendez v. Westminster (1946, 1947) decision to prohibit de jure school segregation for Mexican-origin students. The Mendez ruling, in turn, served as a legal benchmark for later school desegregation cases.