Area Code Atlas

NANP-Overlay of 310 (California) Numbering Plan Area (NPA) with 424 NPA

310 NPA Splits, Creating 424 NPA (California)

NPA 424 overlay on 310 announced

NPA 424 to Overlay NPA 310 (California)

Permissive 1+10-digit dialing begins for 310/424 overlay

On December 31, 2005, customers in the 310 and 424 area codes began permissive dialing of 1 + area code + seven-digit number for calls between area codes, including calls between 310 and 424. This transition prepared callers for the upcoming overlay and mandatory ten-digit dialing.

NPA 424 overlays 310

Area code 424 was introduced as an overlay to the entire 310 region on July 26, 2006, marking California's first area code overlay. The overlay allowed new numbers to be assigned with the 424 code in the same geographic area as 310. This change affected West Los Angeles and South Bay, Los Angeles County, CA.

Mandatory 1+10-digit dialing for 310/424 overlay

Beginning July 26, 2006, mandatory 1 + area code + seven-digit dialing was required for all calls within the 310 and 424 area codes, coinciding with the implementation of the 424 overlay.