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 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: