What was the Treaty of Guadalupe Hidalgo?

The Treaty of Guadalupe Hidalgo was the 1848 peace treaty that ended the Mexican-American War, transferring about 525,000 square miles of Mexican territory to the United States in exchange for 15 million dollars and the assumption of about 3.25 million dollars in American citizen claims against Mexico. The treaty was signed on February 2, 1848 in the Villa de Guadalupe Hidalgo, a town just north of Mexico City named for the Virgin of Guadalupe. American diplomat Nicholas Trist negotiated for the United States, and Mexican commissioners Bernardo Couto, Miguel Atristain, and Luis Cuevas signed for Mexico.

The story of the negotiation is unusual. Trist had been recalled by President James K. Polk in October 1847 because Polk believed Trist was being too lenient. Trist nonetheless ignored the recall, continued negotiating, and presented the signed treaty as a fait accompli. Polk submitted it to the Senate anyway because the political costs of continuing the war or repudiating Trist exceeded the costs of accepting his work. The Senate ratified the treaty on March 10, 1848 by 38 to 14 with both expansionists and antislavery senators voting against.

The treaty had 23 articles. Article V established the new boundary along the Rio Grande from the Gulf of Mexico to its junction with the western boundary of New Mexico, then west and north to the Pacific. Article VIII gave Mexicans living in the ceded territories one year to declare Mexican citizenship; those who did not were considered to have elected United States citizenship and were guaranteed the rights of property and conscience. Article IX promised that they would be admitted to American citizenship and enjoy the rights of citizens of the United States as soon as practicable, language that turned out to be vague enough to be widely violated.

Article XII required the United States to pay 15 million dollars to Mexico over installments. Article XIII required the United States to assume claims of American citizens against Mexico totaling no more than 3.25 million dollars. Article XI committed the United States to suppress raids by Native peoples from American territory into Mexico, an obligation later ignored and then formally erased by the Gadsden Purchase.

The treaty preserved Mexican land grants, but in practice American courts often invalidated them or made litigation prohibitively expensive, and most Spanish and Mexican land grants in California, New Mexico, and Texas were eventually transferred to American owners. The treaty established the present southern border of the lower 48 states except for the small area added by the Gadsden Purchase of December 30, 1853, and it remains a foundational document of the American Southwest.