925 Area Code: East Bay California — Cities, ZIP Codes & History

The 925 area code covers the eastern portion of the San Francisco Bay Area — Contra Costa County and the Tri-Valley communities of eastern Alameda County. Introduced on March 14, 1998 when it split from the 510 area code, 925 serves a region that has grown dramatically as Bay Area tech workers and remote employees have relocated to its more affordable suburbs.

The 925 zone stretches from the Carquinez Strait in the north to the Livermore Valley in the south — encompassing Concord, Walnut Creek, Antioch, Brentwood, Pittsburg, Livermore, Pleasanton, Dublin, San Ramon, Danville, and Lafayette. This guide covers the 925 area code's geography, cities, ZIP codes, time zone, and how businesses get a 925 number.

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The 925 area code covers two distinct sub-regions of the East Bay: Contra Costa County (the north and central Diablo Valley) and the Tri-Valley (Livermore, Pleasanton, Dublin, San Ramon — in eastern Alameda County). It does not cover the inner East Bay (Oakland, Berkeley, Fremont) — those use 510.

Major Cities Covered by 925

• Concord — Contra Costa County's largest city (pop. 130,000+); BART-accessible, major retail and healthcare hub
• Walnut Creek — affluent commercial centre of Contra Costa; major financial and healthcare services cluster
• Antioch — eastern Contra Costa, one of the county's largest cities
• Brentwood — fastest-growing city in Contra Costa County, eastern agricultural fringe
• Pittsburg — industrial eastern Contra Costa city near the San Joaquin Delta
• Martinez — Contra Costa County seat
• Livermore — Lawrence Livermore National Laboratory; Tri-Valley wine region
• Pleasanton — corporate HQ hub (Workday, Ellie Mae, Safeway HQ legacy)
• Dublin — major commercial growth corridor; BART-connected
• San Ramon — major corporate campus city (AT&T California, Chevron offices, GE Digital)
• Danville — affluent suburban community in San Ramon Valley
• Lafayette, Moraga, and Orinda — affluent Lamorinda communities

Key ZIP Codes in the 925 Area Code

• Concord: 94518, 94519, 94520, 94521, 94522, 94524
• Walnut Creek: 94595, 94596, 94597, 94598
• Antioch: 94509, 94531
• Brentwood: 94513
• Livermore: 94550, 94551
• Pleasanton: 94566, 94588
• Dublin: 94568
• San Ramon: 94582, 94583
• Danville: 94526
• Lafayette: 94549

Time Zone

The 925 area code is in the Pacific Time Zone (PT): UTC−8 during Pacific Standard Time (November through mid-March) and UTC−7 during Pacific Daylight Time (mid-March through early November). California observes daylight saving time.

The 925 area code emerged from the 510, which itself had been split from the 415 San Francisco area code just eight years earlier — a reflection of how rapidly the Bay Area's suburban population grew in the 1990s.

• 1947: All of California assigned area code 213.
• 1951: 415 split for Northern California (San Francisco, Oakland, all Bay Area).
• 1991: 510 split from 415 for the East Bay (Oakland, Berkeley, Fremont, Hayward, Contra Costa County).
• 1998 (March 14): 925 split from 510 for eastern Contra Costa County and the Tri-Valley — effectively the suburban and rural East Bay east of the Berkeley/Oakland hills.
• 1998–present: 925 serves Contra Costa and Tri-Valley; 510 serves the inner East Bay.

The split was driven by the East Bay's explosive growth in the 1990s — BART extension into eastern Contra Costa and the Tri-Valley made bedroom communities viable for Bay Area commuters, rapidly depleting the 510 number pool.

The 925 area code hosts a mix of major corporate campuses, federal research facilities, and a growing healthcare sector — making it a significant business market in its own right, independent of San Francisco or Oakland.

Pleasanton and San Ramon — Corporate Hub

• Workday — cloud HR and financial management, global HQ in Pleasanton
• Ross Stores — discount retail chain HQ in Dublin
• AT&T California — major San Ramon campus
• Chevron — significant San Ramon corporate campus
• 24 Hour Fitness — San Ramon HQ

Livermore — National Labs and Wine

• Lawrence Livermore National Laboratory (LLNL) — major federal research facility, nuclear security and energy research, ~8,000 employees
• Sandia National Laboratories — Livermore satellite campus
• Livermore Valley wine region — 50+ wineries in the appellation

Healthcare

• John Muir Health — major Contra Costa health system, headquartered in Walnut Creek
• Kaiser Permanente — multiple 925-area hospitals and medical centres
• Sutter Health — Antioch and Concord presence

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A local 925 number signals an East Bay or Tri-Valley presence — highly credible for businesses selling into Pleasanton's corporate campuses, Walnut Creek's financial and healthcare services sector, or the Contra Costa County government market.

Cloud phone platforms provision 925 numbers in minutes. No physical Contra Costa or Tri-Valley office is required. MeraTalk supports 925 virtual number provisioning and porting across all plans — with auto-attendant, call recording, voicemail-to-email, and CRM integration included. Browse available 925 numbers at meratalk.com.

925 vs 510 — Which East Bay Code Should You Choose?

• 510 — inner East Bay: Oakland, Berkeley, Fremont, Hayward; stronger association with urban Bay Area
• 925 — outer East Bay: Contra Costa, Tri-Valley; signals suburban East Bay, Pleasanton/San Ramon corporate corridor
• Choose 925 if your target customers are in Contra Costa, Pleasanton, San Ramon, Walnut Creek, or Livermore; choose 510 for Oakland, Berkeley, or inner East Bay markets

Like all US area codes, 925 numbers are spoofed by scammers who want to appear local to Contra Costa or the Tri-Valley. Common impersonation targets include PG&E (Pacific Gas & Electric), Contra Costa County agencies, and local healthcare systems. For more, see 925 area code.

• PG&E never threatens same-day disconnection by phone — hang up on any such call
• Contra Costa County government communicates by mail first; calls demanding immediate payment are scams
• Report suspicious 925 calls to the FCC at fcc.gov/consumers and the California AG at oag.ca.gov

Reaching an East Bay contact from outside the United States follows the standard North American dialing pattern. Callers start with their country's international exit code, add the US country code 1, then the 925 prefix and the seven-digit subscriber number.

• From the UK or most of Europe: dial 00, then 1, then 925 and the seven-digit number
• From Australia: dial 0011, then 1 925 and the number
• From a mobile phone anywhere: dial +1 925 followed by the seven digits — the plus sign replaces the exit code automatically
• From Canada or the Caribbean: dial 1 925 and the number directly, since these countries share the North American Numbering Plan

Remember the time difference before calling. The East Bay runs on Pacific Time, so a morning call from London lands in the middle of the Californian night. Business hours of 9 am to 5 pm PT correspond to 5 pm to 1 am in the UK and 3 am to 11 am on Australia's east coast.

US law gives subscribers the right to keep their phone number when switching carriers, and that protection applies fully to 925 numbers. A Contra Costa or Tri-Valley business that has printed its number on signage, vehicles, and marketing materials can move to a new provider without losing it.

1. 1Request a copy of the current bill or customer service record — the new carrier needs the account number, service address, and authorized contact exactly as the losing carrier has them on file
2. 2Submit the port request through the new provider and sign the letter of authorization
3. 3Keep the old service active until the port completes; cancelling early can void the transfer
4. 4Test inbound and outbound calls once the number goes live, then close the old account

Ports between cloud providers typically complete within a few business days, while moves away from legacy copper lines can take longer. Geography does not block the process — a business relocating out of California can port its East Bay number to a cloud platform and keep answering local calls from anywhere.

In an era of national toll-free lines and web chat, a local prefix remains one of the simplest trust signals a business can display. Residents of Walnut Creek, Concord, or Pleasanton are far more likely to answer a call that looks like it comes from their own community than one from an unfamiliar region or an unlabeled toll-free number.

• Higher answer rates — recipients associate the prefix with neighbors, schools, local clinics, and hometown businesses
• Local search credibility — a matching phone prefix reinforces business listings and map profiles for East Bay searches
• Community positioning — service businesses competing against national chains can lead with their local identity
• Consistent branding — one recognizable local number works across ads, signage, and directories for years

For companies selling into the San Ramon and Pleasanton corporate corridor, a local presence number also smooths outreach — procurement teams and office managers screen unfamiliar callers heavily, and a familiar prefix helps a legitimate call get picked up.

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