The 310 area code is the Los Angeles Westside and South Bay — Santa Monica, Beverly Hills, Malibu, Culver City, Torrance, the beach cities, and Catalina Island — carved out of 213 in November 1991 and sharing its territory with the 424 overlay since 2006.
No other area code in California was fought over harder. The Westside spent the better part of a decade resisting every plan that threatened its three digits, and the code came out of that fight with something few NPAs have: a market reputation. Here is where 310 sits, why the 424 battle happened, and what the two codes mean side by side today.
The map behind the reputation
310’s footprint is the coastal arc of Los Angeles County: Santa Monica, Beverly Hills, Malibu, Westwood, Brentwood, Venice, and Culver City on the Westside; El Segundo, Manhattan Beach, Hermosa Beach, Redondo Beach, Torrance, and Inglewood down the South Bay; LAX in between; and Santa Catalina Island about twenty-two miles offshore. Downtown and Hollywood sit next door under 213 and 323, with the San Fernando Valley across the hills on 818.
That geography is why the code acquired a signature quality. The entertainment industry’s Westside offices, the beach cities, and Beverly Hills all answer under the same three digits — and for thirty-plus years, a 310 display has read as shorthand for that stretch of the coast.
Two splits built it
310 exists because 213 ran out of room. The 1947 numbering plan gave one code to all of southern California; by the late 1980s, LA County’s growth had exhausted it again, and the CPUC ordered another split — the fourth carve-out from the original 213 territory. On November 2, 1991, the Westside, South Bay, and a broad southern swath of the county moved to 310 while downtown kept 213.
Growth didn’t stop. On January 25, 1997, 310 itself was split: the southeast portion of the county — Long Beach and its neighbors — moved to the new 562 code, leaving 310 with the coastal core it holds today.
The fifteen-year war over 424
Then came the fight. In May 1998 the CPUC approved what would have been California’s first-ever overlay, adding 424 on top of 310 with mandatory 1+10-digit dialing. Westside customers revolted — at the dialing change and at the idea of a second code on their territory. A petition led by Assemblyman Wally Knox succeeded: in 1999 the Commission suspended the 424 activation weeks before launch, rolled back mandatory ten-digit dialing, and turned to number pooling to stretch the existing supply.
The reprieve kept getting extended. In 2000 the CPUC adopted a geographic split instead — which would have forced half the region to change numbers — then concluded in 2003 that even the split wasn’t yet necessary. Pooling bought seven years. Finally, in August 2005, the Commission rescinded the split plan and approved an all-services overlay: mandatory 1+10-digit dialing began July 26, 2006, and the first 424 numbers were issued on August 26, 2006 — the first overlay ever implemented in California. The full docket trail lives in the CPUC’s published decisions.
310 versus 424 today
The overlay’s mechanics are the standard ones our area code guide covers: nobody’s number changed, both codes cover the identical footprint, and calls between them are local. New assignments draw from whichever pool has stock — which increasingly means 424, because 310’s prefixes are the scarce, long-held ones.
That scarcity is where the perception gap lives. A 310 number generally signals a line established before supply tightened; a 424 number signals a newer one. Businesses sometimes hunt for remaining 310 inventory for exactly that reason. Mechanically, though, the codes are interchangeable — same rates, same coverage, same localness — and a 424 caller is every bit as Westside as a 310 one.
When an unknown 310 or 424 number calls
Treat the prestige as marketing, not evidence. Scammers like recognizable codes precisely because people trust them, and caller ID spoofing can paint 310 on a call from anywhere — including “neighbor spoofing” that copies your own code and prefix to bait an answer. Numbers also port and travel legitimately, so the display never proves a location in either direction.
The habit that screens calls in any market applies here: say nothing sensitive to an inbound caller; hang up and redial the organization on a number you find yourself. An area code is a routing artifact, not a trust signal.
Holding a Westside number as a business
For companies selling into west LA, a 310 or 424 number is a local presence asset — coastal LA customers recognize and answer coastal LA numbers. Availability is the practical question: 424 stock is provisioned immediately, while genuine 310 inventory depends on what specific rate centers still hold.
SIPNEX stocks Westside and South Bay DID inventory by rate center, pairs a 310 or 424 line with hosted extensions from $6.99/mo, delivers it over SIP trunking, and signs every call A-level under its own STIR/SHAKEN certificate.
Frequently asked questions
Which cities still use the 310 area code?
Santa Monica, Beverly Hills, Malibu, Culver City, Westwood, Venice, Inglewood, El Segundo, the beach cities, Torrance, and the rest of the LA Westside and South Bay — plus Catalina Island. Since August 2006 the same Westside territory has also been served by the 424 overlay, which shares the footprint exactly. Downtown LA next door uses 213 and 323.
Why did the 424 overlay take so long to arrive?
Because the region fought it. The CPUC approved 424 in 1998, but public opposition to a second code and mandatory 1+10-digit dialing led the Commission to suspend the launch in 1999 and stretch 310’s supply with number pooling. A geographic split was adopted in 2000, then deferred in 2003, and the overlay was finally implemented in mid-2006 — mandatory ten-digit dialing on July 26, first 424 numbers on August 26 — California’s first.
Can I still get a 310 number instead of a 424 one?
Sometimes. 310 prefixes are largely assigned, so availability depends on which rate centers still hold inventory; most new Westside assignments draw from 424. Carriers that provision by rate center, like SIPNEX’s DID service, can check specific 310 stock — but a 424 number covers the identical territory.
Does a 424 number mean the caller is outside Los Angeles?
No. 424 is a full overlay of 310’s footprint — a 424 caller is as local to Santa Monica or Torrance as a 310 one, just on a newer line. And neither code proves location anyway: numbers port, VoIP dials from any city, and displays can be spoofed. Verify callers by calling back on a published number.
Is Catalina Island really in the 310 area code?
Yes. Santa Catalina Island, about twenty-two miles off the coast, has been part of the 310 numbering area since the code was created in 1991, and the 424 overlay covers it too. Avalon’s phone numbers are as much a part of the Westside pool as Beverly Hills’.
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