Treaty of Guadalupe Hidalgo (1848): Mexico Cedes the Southwest

The Treaty of Guadalupe Hidalgo, signed on 2 February 1848, ended the Mexican-American War. Mexico ceded about 525,000 square miles of territory, including California and New Mexico, and accepted the Rio Grande as the border of Texas, in return for 15 million dollars. Negotiated by an American envoy who had been ordered home, it fixed most of the modern US-Mexico border and made some 80,000 to 100,000 Mexicans residents of the United States almost overnight.

Background

By September 1847 US forces under General Winfield Scott had captured Mexico City (see Mexican-American War). Santa Anna resigned the presidency, and a provisional Mexican government under Manuel de la Peña y Peña moved to the city of Querétaro. Mexico was occupied, divided and bankrupt, but many Mexican politicians still opposed giving up territory.

President James K. Polk had sent Nicholas Trist, chief clerk of the State Department and a fluent Spanish speaker, to travel with Scott’s army and negotiate when the moment came. Early talks in August and September 1847 failed. In October Polk, frustrated and under pressure from expansionists who wanted to take even more of Mexico, recalled Trist.

A defiant envoy

The recall reached Trist in November 1847. Convinced that a chance for peace would be lost if he left, and encouraged by Scott and the British diplomat Edward Thornton, he decided to stay. He explained his reasons to the secretary of state in a letter of around 65 pages and reopened talks with three Mexican commissioners, Luis G. Cuevas, Bernardo Couto and Miguel Atristáin.

The treaty was signed on 2 February 1848 in the town of Guadalupe Hidalgo, just north of Mexico City, near the shrine of the Virgin of Guadalupe. Nine days earlier, unknown to either side, gold had been discovered in California, which was about to change hands.

Main terms

• Border: The boundary ran up the Rio Grande from its mouth, then west along the southern edge of New Mexico and the Gila River to the Colorado River, and from there to the Pacific just south of San Diego.
• Territory: Mexico ceded Alta California and New Mexico, known as the Mexican Cession, and gave up its claim to Texas.
• Payment: The United States paid 15 million dollars and assumed up to 3.25 million dollars in claims by its citizens against Mexico.
• Citizens: Mexicans in the ceded lands could keep their property and choose, within one year, to remain Mexican citizens; otherwise they would become US citizens.
• Raids: Article XI committed the United States to prevent cross-border raids by Native nations into Mexico.

Ratification

Polk was angry with Trist but saw that the treaty met his original aims, and a long war was becoming unpopular. He sent it to the Senate, which approved it on 10 March 1848 by 38 votes to 14. Senators struck out Article X, which would have protected Mexican land grants, and changed other wording. The Mexican Congress ratified the amended treaty in May, after US envoys signed the Protocol of Querétaro explaining that the changes did not cancel valid property rights. Ratifications were exchanged on 30 May 1848, and the last American troops left Mexico City in June.

Trist was dismissed from government service, and his expenses for the mission were not paid until 1871.

Consequences

The treaty transformed the United States into a continental nation reaching the Pacific, and the California Gold Rush soon drew hundreds of thousands of people to the new lands. Whether slavery would be allowed there became the central political quarrel of the next decade.

For Mexican Americans in the new territories, the treaty’s guarantees often proved weak. In California the Land Act of 1851 forced owners to prove their titles before a federal commission, a process so slow and expensive that many Californios lost their ranches. Similar disputes over land grants in New Mexico lasted into the 20th century.

The border itself was soon adjusted. The Gadsden Purchase of 1853–1854 added land south of the Gila River and released the United States from Article XI. A joint boundary commission surveyed the line in the early 1850s, and later shifts of the Rio Grande caused the long Chamizal dispute, settled only in 1963.

Timeline

• 1847, 14 September: US troops occupy Mexico City.
• 1847, October: Polk orders Trist’s recall.
• 1847, November-December: Trist decides to stay and resumes talks.
• 1848, 24 January: Gold is discovered at Sutter’s Mill, California.
• 1848, 2 February: The treaty is signed at Guadalupe Hidalgo.
• 1848, 10 March: The US Senate ratifies it, 38-14.
• 1848, 30 May: Ratifications are exchanged at Querétaro.
• 1848, 4 July: Polk proclaims the treaty in force.

Why it matters

The Treaty of Guadalupe Hidalgo redrew the map of North America, giving the United States about half of Mexico’s pre-war territory, counting Texas. It set most of today’s US-Mexico border, shaped the lives of the Mexican communities that suddenly found themselves inside the United States, and remains a key document in debates about land rights and borderland history. In size, it rivals the Louisiana Purchase as one of the largest transfers of land in American history.