Area codes 310 and 424

Area code 310 is a California telephone area code that was split from area code 213 on November 2, 1991. Area code 424 is an overlay of 310 that became effective on July 26, 2006. It is the area code that covers West Los Angeles and South Bay areas of Los Angeles County, including Santa Catalina Island (located 26 miles (42 km) south of the mainland portion of Los Angeles County). It also includes a small portion of Ventura County. Area code 424 is the first non-mobile area code overlay in Southern California. Because of this, dialers in the 310 area code are no longer able to dial a 7-digit number even if they are dialing another phone number in the same area code. Until the overlay of area codes 657 and 714 became active in 2008, the 310-424 complex was the only area code overlay in the entire state of California, despite California having more area codes than any other state.

On January 25, 1997, it was split again, with area code 562 having been created for the southeast portion of Los Angeles County and a portion of Orange County.