• Area Codes and Numbering

  • The North American Numbering Plan (NANP) is the telephone numbering system for the Public Switched Telephone Network in the United States, Canada, and some Caribbean countries. The NANP is divided into smaller Numbering Plan Areas that are each identified by a three-digit code, commonly known as an area code. Telephone numbers in the NANP are structured in the format NPA-NXX-XXXX, in which

     
    NPA is the 3-digit area code that identifies a specific geographic area;

     
    NXX is the 3-digit prefix that identifies a specific central office within an area code; and

     
    XXXX is the 4-digit line number that identifies a specific line within a central office.

     
    The Federal Communications Commission (FCC) has exclusive jurisdiction over telephone numbering in the United States but has delegated specific authority to state regulatory agencies. Tasked with the authority granted by the FCC, the CPUC conducts area code relief and implement number conservation measures in accordance with FCC policy.

     
    As of September 2018, California has 34 area codes. A new area code is introduced to a geographic area when there are no more three-digit prefixes available in the existing area code.

     
    In recent years, growing consumer demand for advanced technologies and smart devices has led to increasing consumption of telephone numbers. As a result, telephone prefix shortage has occurred in many locations, resulting in the need to add new area codes.

     

    Area codes are introduced in the form of a geographic split or an overlay. In the last ten years, California has introduced ten area codes using the overlay method.

     

    Existing Area Code 

    Locality 

    Area Code Introduced   Effective Date Form
    805 Oxnard, Santa Barbara and San Luis Obispo Counties 820 6/30/2018 Overlay
    619 San Diego County 858 6/19/2018 Overlay  
    916 Sacramento County 279 3/10/2018 Overlay  
    323 Southern California 213 8/01/2017 Overlay  
    415 San Francisco County, most of Marin County and small portion of San Mateo County 628 3/21/2015 Overlay  
    408 Most of Santa Clara County and small portions of Alameda and Santa Cruz Counties 669 11/20/2012 Overlay  
    760 Far southeastern third of California 442 11/21/2009 Overlay 
    818 San Fernando Valley area of Los Angeles County 747 5/18/2009 Overlay
    714 Orange County 657 9/21/2008 Overlay  
    310 Los Angeles County 424 8/26/2006  Overlay  

     

    On June 21, 2018, the CPUC ordered an overlay for the 510 area code in Alameda and Contra Costa Counties.  The new 341 area code will be introduced on July 22, 2019.  The 909 area code is the next area code to be depleted of available prefixes.  The 909 area code is projected to run out of available prefixes by September 2021.

     


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