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Skip Navigation LinksPUC > Communications > General Communications Information > Area Codes > 310/424 Area Code History

310/424 Area Code Background and History

The 310 area code was created in late 1991 to provide more telephone numbers in the 213 area code. Both the 213 and the 310 serve communities in Los Angeles County. In January 1997, the 310 area code was itself split forming a separate 562 area code, again to replenish the supply of numbers. On February 18, 1998, the telecommunications industry submitted to the Commission another proposed relief plan for the 310 area code, claiming a near-term shortage of telephone numbers.

On May 7, 1998, the Commission issued D.98-05-021, approving a 310 area code relief plan, calling for implementation of the first area code overlay ever approved within California. In conformance with federal rules, the overlay plan also required implementation of mandatory 1+10-digit dialing within both the existing 310 area code and the newly created 424 area code.

On June 9, 1999, shortly after implementation of mandatory 1+10-digit dialing, Assemblyman Wally Knox, along  with other parties, petitioned to modify D.98-05-021, seeking to halt the opening of the overlay scheduled to occur on July 17, 1999, and to end mandatory 1+10-digit dialing. In D.99-06-091, issued on June 24, 1999, the Commission temporarily suspended mandatory 1+10-digit dialing in order to provide time to address the full merits of the Petition.

In D.99-09-067, September 16, 1999, the Commission granted the Knox Petition, suspending the 310 area code overlay plan, eliminating mandatory 1+10-digit dialing, and instituting a program of number pooling and related conservation measures to extend the 310 area code life.  D.99-09-067 also ordered the staff to undertake a study of 310 area code number utilization to determine how efficiently carriers were actually using numbering resources already assigned to them. The Commission stated that a full accounting of 310 area code numbers actually in use would be required before setting any further date for the opening of a new area code.

D.99-09-067 also adopted number conservation and assignment reporting requirements to utilize numbering resources more efficiently.  Rules adopted in D.99-09-067 enabled the Commission to make significant progress in more efficient utilization of existing numbering resources, extending the life of existing area codes and delaying implementation of new area codes.

On March 16, 2000, complying with a directive in D.99-090-067, the Commission's Telecommunications Division issued its "Report on the 310 Area Code”, which presented findings on the efficiency of   number use in the 310 area code.  The report stated that approximately three million unused numbers remained in the 310 area code as of November 1999.   The CPUC solicited comments on the Report from parties and the public.  

Because the FCC required a back-up plan in conjunction with the implementation of number conservation measures, the CPUC issued D.00-09-073, adopting as a back up plan, a geographic split for the 310, dividing the code along a line between Inglewood/Los Angeles Airport and El Segundo/Hawthorne.

The CPUC continued to be the subject of petitions from telephone companies, concerned that a shortage of numbers would curtail their efforts to sell services to customers.

 In August 2000, wireless carriers submitted a request to the CPUC, asking for implementation of a new area code in the 310.  In response to that petition, and as required by CPUC D.00-09-073 , on February 16, 2001, CPUC staff issued an audit report on the accuracy and reliability of the data submitted by the telecommunications companies regarding their utilization of numbers  in the 310 area code. Staff found that available telephone numbers were under reported and therefore far more numbers were available than industry projections had estimated.

Staff offered recommendations for efficient and accurate management of telephone numbers.  In addition, due to the underreporting of available telephone numbers, staff found that there were enough numbers in the 310 area code to meet the needs of telephone consumers and providers for the foreseeable future and that a new area code was not necessary.

On October 2003, the CPUC decided that an area code split is unnecessary because an adequate supply of telephone numbers existed in the 310 area code. Instead, the CPUC decided it would closely monitor the supply of telephone numbers in the 310 area code.

On March 9, 2005, carriers Cingular Wireless, Nextel of California, SBC California, Sprint, T-Mobile, Verizon Wireless and Verizon California Inc filed a petition to modify D.00-09-073.


On August 25, 2005, the CPUC responded by issuing D.05-08-040, modifying D.00-09-073, and ordering the implementation of an all services area code overlay for the 310 beginning August 26, 2006.  This overlay, along with the CPUC-ordered public education plan, has been implemented in 310 with 1 + ten digit dialing effective July 26, 2006 and numbers with the 424 area code have been assigned as of August 26, 2006.  Details of the 310 public education plan are available on this website.


Last Modified: 2/4/2009

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