The treaty that formally ended the Mexican-American War in 1848 is the Treaty of Guadalupe Hidalgo. The war lasted from 1846 to 1848 and was primarily sparked by the annexation of Texas and territorial disputes. Under this treaty, Mexico ceded a significant portion of its northern territories, including present-day California, Nevada, Utah, Arizona, and parts of Colorado and New Mexico, to the United States. In exchange, the U.S. paid Mexico $15 million and assumed certain claims by American citizens against Mexico. This treaty significantly expanded U.S. territory and fueled debates over slavery's expansion into the new territories.