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 October 2012 there are 31 area 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 |
July 26, 2006 |
Overlay |
| 714 |
Orange County |
657 |
February 23, 2008 |
Overlay |
| 818 |
San Fernando Valley area of Los Angeles County |
747 |
October 2, 2008 |
Overlay |
| 760 |
Far southeastern third of California |
442 |
May 2, 2009 |
Overlay |
415 Area Code
408 Area Code
760 Area Code
818 Area Code
310 Area Code
Area Code Reports
Area Code Forcast October 2012
Frequently Asked Questions about Area Code Changes
California Telephone Boundaries Map and Other Information
North American Numbering Plan Administration