The document that ended the Mexican-American War and defined the border between the two nations is the Treaty of Guadalupe Hidalgo, signed on February 2, 1848. This treaty concluded the conflict, which stemmed from territorial disputes following the U.S. annexation of Texas. Under the terms of the treaty, Mexico ceded a vast portion of its territory, including present-day California, Arizona, New Mexico, and parts of Colorado, Utah, and Nevada, to the United States. In exchange, the U.S. paid $15 million and assumed certain claims against Mexico. The treaty significantly expanded U.S. territory and shaped future relations between the two nations.