Atlas of Hispanic-American History

MANIFEST DESTINY AND HISPANIC AMERICA 91

The U.S. Invasion of Mexico, 1846–1848

At the heart of the U.S.-Mexican War lay the dispute over the size of Texas. After annexing the Lone Star Republic—as independent
Texas was called—the United States claimed that the Texas border followed the Rio Grande, not only from the Gulf of Mexico to El
Paso in southwest Texas, but also northward from El Paso to include Albuquerque and Santa Fe in New Mexico as well as parts of
present-day Colorado and Wyoming. When U.S. troops began building a fort just across the Rio Grande from Matamoros, they suc-
ceeded in provoking Mexican troops to fire the first shots. U.S. President James K. Polk used the Mexican action to occupy Mexico
and take New Mexico and California. The major battles and routes of advance by leading American commanders are illustrated in
the map above.