310/424 Area Code

On August 25, 2005, the California Public Utilities Commission (CPUC) approved an overlay in Decision 05-08-040 to accommodate the need for additional telephone numbers in the 310 area code region. On August 26, 2006, the overlay became effective and the new 424 area code was overlaid onto the 310 area code.

The overlay allowed all existing 310 area code customers to keep their telephone numbers and the 310 area code. However, calls made from the 310 or 424 area code need to be dialed as 1 + area code + 7-digit telephone number. Calls placed from 310 or 424 numbers without the “1” and the area code will not be completed and will result in a recording instructing the caller to hang up and dial again. Cellphone callers who have service with certain cell service providers may be able to complete calls without dialing “1” before the area code.

Dialing 1 + area code + 7-digit telephone number does not change what a call costs and does not mean that a call is a toll or long distance call. Therefore, calling areas and rates do not change. What is a local call before the overlay remains a local call after the overlay and dialing “1” and the area code does not mean there is a charge for the call. Calls to 911, as well as 211, 311, 411, 511, 611, 711 and 811 are not affected, and continue to be dialed with 3 digits.


The 310 area code was created when it was split from the 213 area code in 1992. In 1997, the 310 area code was split to create the 562 area code. In May 1998, the CPUC issue D.98-05-021, approving a 310 area code relief plan and calling for the implementation of the first overlay in California. Customers expressed objections to the overlay and the 1 + 10-digit dialing requirement. Thus, in September 1999, the CPUC adopted D.99-09-067, suspended 310 area code overlay relief plan, and instituted number pooling and other conservation measures in an effort to delay the exhaust of the 310 area code. In September 2000, pursuant to Federal Communications Commission requirements, the CPUC issued D.00-09-073 and approved a split for the 310 area code as a backup relief plan, but deferred implementation of the split and ordered an audit of the 310 area code number utilization data reported by carriers. In February 2001, Commission staff issued an audit report that found far more available numbers in the 310 area code than reported by carriers. In October 2003, the CPUC adopted D.03-10-060, ruling that a split was unnecessary at the time as there were adequate numbers in the 310 area code to meet carrier and customer demands. In March 2005, carriers filed a petition to replace the previously approved geographic split with an overlay as the adopted back-up plan for the 310 area code. On August 25, 2005, the CPUC responded to the petition by issuing D.05-08-040, ordering an overlay for the 310 area code. The overlay was implemented on August 26, 2006, adding the 424 to the 310 area code.
Today the 310 and 424 area codes serve the Westside and South Bay area of Los Angeles County and a small portion of Ventura County.

Map of the 310/424 area code territory

Immigration Guide