Area Code 510

California

Area code 510 serves California, primarily Oakland, in the Pacific Time (PT) time zone. It has served the region since 02-Sep-1991.

Published: February 17, 2026Verified against NANPA and FCC records

Overlay Area Code

This area code shares its geographic footprint with an overlay code, so the same cities are served by two area codes. Because overlays leave existing numbers untouched, this region's relief planning favors adding codes over redrawing boundaries.

The codes serving this same region: area code 341 (Oakland).

With prefix utilization already at 98.1%, numbering resources here are under sustained pressure — context that explains why overlays were introduced.

In service since: 02-Sep-1991

Learn more about overlay and split area codes →

Area Code Splits

One area code has been carved out of this code's original territory through a geographic split. Each split was a relief action: as demand grew, part of the region was reassigned to a new code rather than overlaying the whole territory.

Split into: area code 925 (Concord).

Learn more about overlay and split area codes →

Demographics & Economics

Demographic Data Unavailable for Area Code 510

County-level demographic data is not available for this area code because NPA boundary polygons are not publicly distributed by NANPA. We use geographic boundary data from the Colorado Open Data Portal to map area codes to counties, which currently covers 194 of 376 geographic area codes.

Demographic statistics (population, income, education, poverty) require county-level aggregations from Census ACS data. Without a county mapping, these aggregations cannot be computed. We are actively seeking additional data sources to improve coverage.

Statistics are population-weighted aggregations from Census ACS 5-year estimates where county boundary data is available.See Sources for details.

Time Zone

Pacific Time (PT)

NANPA Relief Status

According to the latest NANPA analysis (July 2026), this area code is not currently listed as exhausting within the next 36 months. No relief planning is in progress for this NPA.

Source: NANPA NPA Relief Planning Reports · See all relief planning statuses

Current Time

Pacific Time (PT)

Prefix Utilization

Geographic Coverage

State

Major Cities

Oakland
Fremont
Hayward
Berkeley
Richmond
San Leandro
Alameda
Union City
Castro Valley
Newark
San Pablo
San Lorenzo
Hercules
El Cerrito
Ashland
Albany
Pinole
Cherryland
Emeryville
Piedmont
Fairview
Rodeo
Kensington
Tara Hills

and 11 more cities

Area Code 510 geographic coverage map (light mode)

Demographics

Detailed demographic and economic data is not yet available for area code 510.

History

Area code 510 was established in 1991 as a geographic area code. Over time, area code area code 925 was split from 510. It shares its territory with area code area code 341.

County Coverage

Population-weighted county share based on aggregated ZCTA population (100% = total mapped population for area code 510).

County	Population	Share
Alameda, CA	1,406,448	77.7%
Contra Costa, CA	339,270	18.8%
San Francisco, CA	63,517	3.5%

Area Code 510 Family Tree

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Total Codes

Splits

Overlays

Max Depth

All Descendants

Code ▲	State	Type	In Service	Parent
341	CA	overlay	22-Jul-2019	510
925	CA	split	14-Mar-1998	510

Area code 510 was originally assigned in 02-Sep-1991 to serve CA. Over the years, it has generated 2 descendant area codes through a combination of geographic splits and overlays as demand for telephone numbers grew.