• Area Codes and Numbering

  • Under the North American Numbering Plan, telephone numbers in the United States, Canada and the Caribbean are structured as a three digit area code, a three digit prefix or code and a four digit line number. Any device requiring interconnection to the public switched telephone network requires an area code, prefix and line number. Devices requiring interconnection are not limited to telephones but include cars equipped with Onstar, ATM’s, burglar alarms and many other systems that would not be considered a telephone.

    An area code is a three-digit number assigned to a geographical area in the United States, Canada, and the Caribbean, used before a seven-digit telephone number when placing a call to, and sometimes from within, that area. As of July 2015, there are 32 codes assigned to California. New area codes are introduced when there are no more three digit prefixes available for assignment. Once an area code no longer has any whole prefixes, it is considered to be at exhaust.  Area codes projected to exhaust in the coming years are:

     

    Area Code exhaustion projections

     Area Code

     Exhaust Date  

    805

    December 2017  

    619

    December 2018  

    510

      June 2018

    909

    March 2019

     

    Area codes are introduced in the form of a geographic split or an overlay. New area codes introduced in California in the past 5 years are as follows:

     

    Old Area Code

    Locality

    New Area Code

    Effective Date

    Form

    916 Sacramento 279 September 2017 Overlay
     323   Southern California 213 January 2017 Overlay

    310

    Los Angeles County

    424

    August 26, 2006

    Overlay

    714

    Orange County

    657

    September 23, 2008

    Overlay

    818

    San Fernando Valley area of Los Angeles County

    747

    May 18, 2009

    Overlay

    760

    Far southeastern third of California

    442

    November 21, 2009

    Overlay

    408

    Most of Santa Clara County and small portions of Alameda and Santa Cruz Counties

    669

    November 20, 2012

    Overlay

    415

    San Francisco County, most of Marin County and small portion of San Mateo County

    628

    March 21, 2015

    Overlay

     

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