New Mexico currently utilizes 2 area codes. When first established by AT&T and the Bell System in 1947, 505 covered the entire state of New Mexico. The most recently added was 575 in 2007. Today, 505 is the most populated with an estimated 1.2 million of the state's 2.1 million residents.
Sources: North American Numbering Plan Administration (NANPA), telecom providers, and the U.S. Census Bureau.