As a result of the Mexican-American War, the United States acquired land in the Southwest known as the Mexican Cession. The Treaty of Guadalupe Hidalgo, signed on Feb. 2, 1848, ended the conflict and resulted in Mexico ceding over 500,000 square miles of territory.
Like the United States, Mexico was a relatively young country, having only established independence from Spain in 1821. The two nations were at war from 1846 to 1848 over terrain in the present-day southwestern United States of America. Texas and California were especially desired by the United States; Texas for its agricultural possibilities and California because it represented the possibility of a coast-to-coast nation. The United States defeated Mexico in 1848.
The Treaty of Guadalupe Hidalgo brought a formal end to the war, and Mexico had to give up land rights. This came to be known as the Mexican Cession. The treaty transferred ownership of present-day California, New Mexico and Arizona and parts of Utah, Nevada and Colorado to the United States. In addition, Mexico relinquished its claim to Texas, and the agreement specified that the Rio Grande River would become the southern boundary of the United States. In exchange, Mexico was paid $15,000,000 for the U.S. boundary extension