The document signed at the end of the Mexican-American War in 1848 is the Treaty of Guadalupe Hidalgo. This treaty formally ended the conflict between the United States and Mexico after a contentious war that lasted from 1846 to 1848. As a result of the treaty, Mexico ceded a vast portion of its northern territories to the United States, including present-day California, Arizona, Nevada, Utah, and parts of Colorado and New Mexico. The treaty significantly increased U.S. territory and further fueled the debate over slavery in the newly acquired lands, deepening sectional tensions that would eventually lead to the American Civil War.