Gadsden Purchase

(Dec. 30, 1853) U.S. purchase of land in Mexico. Following the conquest of much of northern Mexico in the Mexican War (1848), advocates of a southern transcontinental railroad endorsed the purchase of 30,000 sq mi (78,000 sq km) of northern Mexican territory, now southern Arizona and southern New Mexico. The purchase was negotiated by James Gadsden, U.S. minister to Mexico, for $10 million. The acquisition fixed the borders of the later 48 contiguous states.