Treaty of Guadalupe Hidalgo signed

On February 2, 1848, American diplomat Nicholas Trist and Mexican commissioners Luis G. Cuevas, Bernardo Couto, and Miguel Atristain signed the Treaty of Guadalupe Hidalgo at Guadalupe Hidalgo near Mexico City. The treaty ended the Mexican-American War and required Mexico to cede California and New Mexico while recognizing the Rio Grande as the boundary of Texas. President James K. Polk had already tried to recall Trist, but Polk submitted the signed treaty to the Senate because the agreement delivered the territorial settlement his administration wanted.

The treaty intensified the political struggle over whether slavery would expand into the Mexican Cession acquired in 1848. Northern critics of President Polk had already backed the Wilmot Proviso in 1846, and the new western lands made the proviso fight more urgent by forcing Congress to decide the status of slavery in California, New Mexico, and Utah. Mexican negotiators also pressed for treaty protections for property and civil rights, making the settlement a diplomatic test of how the United States would govern conquered territory.

Senate ratification on March 10, 1848 transformed the Mexican Cession into the central issue of the Compromise of 1850. California statehood in 1850, the territorial governments created for Utah and New Mexico in 1850, and the sectional conflict that followed all grew directly from the land transfer fixed by the Treaty of Guadalupe Hidalgo.