Introduction
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.
Key Takeaways
Covers 925 area code location in depth
Covers East Bay area code in depth
Covers Contra Costa area code in depth
Covers Walnut Creek phone number in depth
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Learn moreWhere Is the 925 Area Code?
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.
History of the 925 Area Code
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.
Major Employers and Economy in the 925 Zone
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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How to Get a 925 Area Code Number
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
Scam Awareness: 925 Area Code Calls
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.
- 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
Conclusion
The 925 area code covers the outer East Bay — Contra Costa County and the Tri-Valley — on Pacific Time, serving Concord, Walnut Creek, Antioch, Livermore, Pleasanton, Dublin, San Ramon, and Danville. Home to Workday, Lawrence Livermore National Laboratory, John Muir Health, and a growing corporate corridor, 925 is a significant Bay Area business market in its own right.
Activate a 925 virtual number and establish your East Bay California presence from anywhere. Browse available 925 numbers at meratalk.com.
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