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. NANPA numbering resources are administered by the North American Numbering Plan Administrator (NANPA). 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 enforces number conservation in California in accordance with Public Utilities Code Section 7930-7943.

 
As of August 2019, California has 35 area codes. A new area code is added 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 added in the form of a geographic split or an overlay. California has added eleven area codes using the overlay method since 2006.

On June 13, 2019, the CPUC ordered an overlay that will add the 840 area code to the existing 909 area code, which serves the southwestern portion of San Bernardino County, the eastern portion of Los Angeles County, and small portions of Orange and Riverside Counties.