May 13, 1846: The Mexican-American War Begins
On this day in 1846, U.S. Congress declared war on Mexico. The Mexican-American War was a defining event for both nations, transforming a continent and forging a new identity for its peoples. By the war’s end in 1848, Mexico had lost nearly half of its territory (the present American Southwest from Texas to California) and the United States had become a continental power.
Explore a timeline of the Mexican-American war to learn about events that preceded the war, its battles, and the aftermath.
Image: Battle of Veracruz during the Mexican-American War. 1851 Painting by Carl Nebel.
When the border crossed people.