The Mexican Cession of 1848 refers to the lands ceded or surrendered to the United States by Mexico at the end of the Mexican–American War. The territory became the states of California, Nevada, Utah and Arizona. It was agreed to in the Treaty of Guadalupe Hidalgo, which formally ended the war (1847–1848) between Mexico and the United States. The treaty was signed on 2 February 1848. The Cession added 500,000 square miles (1,300,000 km2) of territory to the southwestern United States. It also contributed to the United States emerging as a world power in the late the 19th century.