Mexico, claiming that the boundary was the Nueces River to the northeast of the Rio Grande, considered the advance of Taylor’s army an act of aggression and in April 1846 sent troops across the Rio Grande. Polk, in turn, declared the Mexican advance to be an invasion of U.S. soil, and on May 11, 1846, asked Congress to declare war on Mexico, which it did two days later.
After nearly two years of fighting, peace was established by the Treaty of Guadalupe Hidalgo, signed on February 2, 1848. The Rio Grande was made the southern boundary ofTexas, and California and New Mexico were ceded to the United States. In return, the United States paid Mexico the sum of $15 million and agreed to settle all claims of U.S. citizens against Mexico.
Answer Choice A