The outcome of the Mexican-American War (1846-1848) was significant territorial expansion for the United States. The war resulted from tensions over Texas's annexation and disputes regarding the Southern border. Following the U.S. victory, the Treaty of Guadalupe Hidalgo was signed in 1848, whereby Mexico ceded a vast portion of its northern territories to the U.S., including present-day California, Arizona, New Mexico, Nevada, Utah, and parts of Colorado and Wyoming. This expansion fueled debates over slavery’s extension into the new territories, contributing to the rising sectional tensions that eventually led to the American Civil War.