The conflict that resulted from territorial disputes between the United States and Mexico in the 1840s is known as the Mexican-American War. Fought from 1846 to 1848, the war was precipitated by the annexation of Texas by the United States and tensions surrounding the border. Key battles occurred at places like Chapultepec and Buena Vista, ultimately leading to a decisive American victory. The war concluded with the Treaty of Guadalupe Hidalgo, which resulted in significant territorial gains for the U.S., including present-day California, Arizona, New Mexico, Nevada, Utah, and parts of Colorado and Wyoming. This expansion fueled debates over slavery and westward expansion.