Which 1848 treaty ended the Mexican–American War and transferred vast western lands to the United States?

The 1848 treaty that ended the Mexican–American War and transferred vast western lands to the United States was the Treaty of Guadalupe Hidalgo.

The treaty was signed on February 2, 1848, at Guadalupe Hidalgo, then a town near Mexico City. It formally ended the war, which had begun in 1846. Mexico recognized the Rio Grande as the southern boundary of Texas and ceded Alta California and much of its northern territory.

The transferred region included present-day California, Nevada, and Utah, most of Arizona and New Mexico, and portions of Colorado and Wyoming. Mexico ceded about 55 percent of its prewar territory, while the United States agreed to pay Mexico $15 million and assume certain claims by American citizens.

The Senate ratified the treaty on March 10, 1848, and the ratifications were exchanged on May 30. The later Gadsden Purchase of 1853 added land in present-day southern Arizona and New Mexico, so it should not be confused with the 1848 settlement.