CPUC dials up 357 as a new Valley overlay area code

The California Public Utilities Commission approves implementation of an overlay area code for the 559 area code region, projecting 559 phone numbers will run out by September 2025

(tatsianamaphoto on AdobeStock)
Serena Bettis
Published December 30, 2023  • 
11:00 am

CALIFORNIA – Within the next few years, the San Joaquin Valley will be home to a new, second area code: 357. 

The new area code will overlay the region that the 559 area code currently serves, the California Public Utilities Commission (CPUC) announced on Dec. 19 after approving the North American Numbering Plan Administrator’s (NANPA) request for a new code. Available phone numbers using the 559 area code are anticipated to run out in September 2025, at which time new numbers will be assigned the 357 code. 

“The CPUC has acted to ensure that telephone numbers continue to be available to meet the demand in the geographic region served by the 559 area code by approving a second area code (called an overlay) that will provide additional numbering resources while minimizing customer inconvenience,” the CPUC said in a press release.

Area code 559 has served California residents throughout Fresno, Kings, Madera, Mariposa, Merced and Tulare counties since the 209 area code was split in 1998. To meet the needs of the San Joaquin Valley’s growing population, the new 357 area code will serve the same region. 

Existing phone numbers will not be affected by the introduction of the overlay, though residents in the Valley — who often drop the area code when exchanging contact information due to its regional prevalence — will need to form the habit of communicating their full 10-digit phone number to ensure they can be reached properly. 

Additionally, once the overlay code is implemented, all calls regardless of location must be made with the 10-digit phone number that includes the area code.

The CPUC said the price of calls will remain the same, as will the three-digit N11 codes for emergency, information and community services. As the projected time frame for the new area code’s use approaches, the CPUC recommends that San Joaquin Valley residents ensure their personal information includes the 559 area code with their existing phone number. 

This could include contacting security and alarm vendors to update dial-up numbers, reprogramming equipment that uses features like speed dialing and call forwarding and updating stationary and personal checks.

Calling for a new area code

This overlay comes from the projected exhaustion of available prefixes with the 559 area code, which are the first three digits in a phone number. According to the CPUC’s decision made on Dec. 14, the 559 area code had 59 available prefixes remaining as of Dec. 20, 2022; each prefix has 10,000 unique phone line numbers. 

Available prefixes were first projected to be exhausted in the fourth quarter of 2025, but that projection has moved up to the third quarter of 2025. As the area’s population grows, more telephone numbers are needed.

The NANPA is the administrating body of the North American Numbering Plan (NANP). According to its website, it consults with and provides assistance to regulatory authorities, like the CPUC, and national administrators to “ensure that numbering resources are used in the best interests of all participants in the (NANP).”

Part of the NANPA’s role is to track the use of area codes and forecast when codes will run out of available prefixes. If an area code is near exhaustion, the NANPA will work to identify how to relieve the issue, which could involve overlays or splitting the region of an area code, which is when one section of a region continues to issue new phone numbers with the same area code, while the other section starts to use a new area code. 

Phone numbers in the NANP follow a specific format — such as not using prefixes that begin with a zero or a one — and while each prefix has 10,000 line numbers, some prefixes are not used and others are set aside by the Federal Communications Commission (FCC) for special uses. 

According to the decision published by the CPUC, the NANPA distributed a notice of the 559 area code exhaustion to the California Telecommunications Industry on Nov. 23, 2022, with two alternatives for relief. The consensus was that an overlay relief plan would be the best option.

“The Industry supported the all-services distributed overlay because it believes it is the most equitable and consumer-friendly alternative,” the CPUC decision said. 

The decision said that the overlay plan was also preferred because customers would retain their existing phone numbers, customer education and technical implementation would be straightforward and implementation would take less time than a geographic split.

Serena Bettis
General Assignment Reporter