Area code 831 is a telephone area code in the North American Numbering Plan for a small region of the U.S. state of California. The numbering plan area (NPA) comprises Monterey County, San Benito County, and Santa Cruz County. The area code was created in 1998 in an area code split of area code 408.
In 1947, the American Telephone and Telegraph Company (AT&T) devised the first nationwide telephone numbering plan and assigned the original North American area codes. The state of California was divided into three numbering plan areas (NPAs) with distinct area codes: 213, 415, and 916, for the southern, central, and northern parts of the state, respectively.[1] California area codes were reorganized geographically in 1950, so that 916 was assigned to a numbering plan area that comprised only the northeastern part from the Sierra Nevada to the Central Valley. The coastal area to the west was assigned area code 415.[2]
Area code 408 was split from numbering plan area 415 on March 1, 1959. The new numbering plan area included most of Santa Clara, Santa Cruz, Monterey and San Benito Counties.
In 1997, the California/Nevada Code Administrator (C/NCA) advised the North American Numbering Plan Administration (NANPA) of the need for area code relief in the 408 numbering plan area. A geographic area code split had been approved by the California Public Utilities Commission (CPUC) which would install area code 831 for a new numbering plan area comprising the communities of Santa Cruz, Salinas, Monterey, and Hollister. Area code 408 would be retained in Sunnyvale, San Jose, Los Gatos, and Gilroy. The area code split became effictive on July 11, 1998, with a permissive dialing period ending on February 20, 1999.[3]
Due to the relatively small size of the area (in both area and population), exhaustion of 831 is unlikely for the foreseeable future.[4]
The service area of NPA 831 includes Big Sur, Monterey Bay, the Salinas Valley, and the southwestern Santa Cruz Mountains.
Major cities in the area are Salinas, Hollister, Monterey, Santa Cruz and places in the northern Central Coast.[5]