(1846-48), conflict between the United States and Mexico. The revolt and declaration of independence of Texas from Mexico in 1836 eventually resulted in the annexation of Texas to the Union in 1845. Mexico refused to recognize the annexation and disputed the boundary of the Rio Grande. After a still-controversial incident along the border, President
James K. Polk, a proponent of
expansionism and
manifest destiny, asked Congress for a declaration of war. He sent Gen.
Zachary Taylor to invade northern Mexico. Col.
Stephen Kearny led U.S. troops to take New Mexico and California, and Gen.
Winfield Scott led his forces to capture Vera Cruz and Mexico City. All three campaigns were successful.
The
Treaty of Guadalupe Hidalgo ended the war on February 2, 1848. Mexico ceded all claims to Texas, and the United States acquired the lands known as the
Mexican Cession; it also agreed to assume outstanding claims of American citizens against Mexico. The acquisition of new lands intensified the slavery controversy in the United States, raising the question of whether the territories should be slave or free. The debate raged for twelve years, culminating in the Civil War. Participants in the later conflict who received firsthand experience in the Mexican War included
Ulysses S. Grant,
William Tecumseh Sherman,
George B. McClellan,
Robert E. Lee,
Stonewall Jackson, and
Jefferson Davis.
