New Mexico Abbr. NM or N.M. or N.Mex. 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.New Mexican n. & adj.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.New Mexico n (Placename) a state of the southwestern US: high semiarid plateaus and mountains, crossed by the Rio Grande and the Pecos River; large Spanish-American and Indian populations; contains over two-thirds of US uranium reserves. Capital: Santa Fé. Pop: 1 874 614 (2003 est). Area: 314 451 sq km (121 412 sq miles). Abbreviation: N. Mex. or NM (with zip code) Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014New` Mex?ico n. a state in the SW United States. 1,819,046; 121,666 sq. mi. (315,115 sq. km). Cap.: Santa Fe. Abbr.: NM, N. Mex., N.M. New` Mex?i?can, n. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.