A state of the southwest United States on the Mexican border. It was admitted as the 47th state in 1912. Site of prehistoric cultures that long preceded the Pueblo civilization encountered by the Spanish in the 1500s, the region was governed as a province of Mexico after 1821 and ceded to the United States by the Treaty of Guadalupe Hidalgo in 1848. The original territory (established 1850) included Arizona and part of Colorado and was enlarged by the Gadsden Purchase of 1853. Sante Fe is the capital and Albuquerque the largest city.