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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.

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

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

 

323 Area Code

415 Area Code

408 Area Code

760 Area Code

818 Area Code

310 Area Code

Area Code Reports

Area Code Forecast 2015

Frequently Asked Questions about Area Code Changes

California Telephone Boundaries Map and Other Information

North American Numbering Plan Administration

  

Last Modified: 8/3/2015


 
 
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