San Mateo County, California

County seat: Redwood City · Population 743,568 (2025) · 449 sq mi

San Mateo County is the 15th most populous of California's 58 counties, with 743,568 people (2025 estimate). Its county seat is Redwood City. The map shows its 20 cities and towns and the 4 neighboring counties.

Map of San Mateo County, California with cities, towns and the county boundary
San Mateo County, California with its cities and towns, unincorporated communities (CDPs) and neighboring counties. Boundaries: U.S. Census Bureau, 2025. Free to use with attribution (CC BY 4.0).
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San Mateo County facts

County seat
Redwood City
Population (2025 estimate)
743,568 −2.7% since 2020
Land area
449 sq mi 56th largest of 58
Water area
292 sq mi
Population density
1,658 per sq mi
Established
1856
Named after
Matthew the Apostle Christian evangelist and apostle (10-74)
Largest city
San Mateo 103,337
Median household income
$158,855
Cities and towns
20 plus 13 CDPs
ZIP codes
31
Time zone
Pacific
FIPS code
06081

Cities and towns in San Mateo County

San Mateo County has 20 incorporated cities, towns and villages. Populations count the people living inside San Mateo County; cities that cross a county line also list the other counties.

NameTypePopulation 2025Also in
San MateoCity103,337
Daly CityCity101,261
Redwood City (county seat)City82,178
South San FranciscoCity64,941
San BrunoCity42,305
PacificaCity36,890
Menlo ParkCity32,713
Foster CityCity32,411
BurlingameCity31,929
San CarlosCity29,261
East Palo AltoCity28,872
BelmontCity28,752
MillbraeCity22,869
Half Moon BayCity11,287
HillsboroughTown11,206
AthertonTown6,960
WoodsideTown5,181
BrisbaneCity4,656
Portola ValleyTown4,292
ColmaTown1,385

Unincorporated communities (CDPs)

Census-designated places are communities without their own city government; the county provides their services.

CommunityPopulationAlso in
North Fair Oaks13,100
El Granada5,232
Broadmoor4,586
Emerald Lake Hills4,235
West Menlo Park3,634
Montara2,917
Moss Beach2,683
Highlands2,450
Baywood Park1,580
Ladera1,297
La Honda1,269
Pescadero691
Loma Mar309

ZIP codes in San Mateo County

31 ZIP codes reach into San Mateo County. ZIP codes ignore county lines, so some also cover a neighboring county.

Population of San Mateo County, 2020–2025

San Mateo County shrank by 20,940 people (−2.7%) between April 2020 and July 2025: 12,212 more births than deaths and a net loss of 32,120 people from migration.

Year (July 1)Population
2020762,639
2021739,463
2022732,245
2023733,949
2024740,627
2025743,568

Neighboring counties

Printable San Mateo County map

The PDF is a vector file with real text: it prints sharp on Letter paper and you can search it for a town. The PNG is 2400 pixels wide for slides and documents. Both are free to use with a credit to WhichCounty.

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Sources

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