Contra Costa County, California

County seat: Martinez · Population 1.2 million (2025) · 717 sq mi

Contra Costa County is the 9th most populous of California's 58 counties, with 1,170,070 people (2025 estimate). Its county seat is Martinez. The map shows its 19 cities and towns and the 7 neighboring counties.

Map of Contra Costa County, California with cities, towns and the county boundary
Contra Costa 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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Contra Costa County facts

County seat
Martinez
Population (2025 estimate)
1,170,070 +0.4% since 2020
Land area
717 sq mi 51st largest of 58
Water area
87 sq mi
Population density
1,632 per sq mi
Established
1850
Named after
opposite coast
Largest city
Concord 123,261
Median household income
$127,229
Cities and towns
19 plus 34 CDPs
ZIP codes
49
Time zone
Pacific
FIPS code
06013

Cities and towns in Contra Costa County

Contra Costa County has 19 incorporated cities, towns and villages. Populations count the people living inside Contra Costa County; cities that cross a county line also list the other counties.

NameTypePopulation 2025Also in
ConcordCity123,261
AntiochCity118,958
RichmondCity114,861
San RamonCity86,209
PittsburgCity77,542
Walnut CreekCity70,012
BrentwoodCity66,607
OakleyCity47,583
DanvilleTown43,302
Martinez (county seat)City36,849
Pleasant HillCity34,017
San PabloCity31,678
HerculesCity26,326
El CerritoCity26,121
LafayetteCity25,313
OrindaCity19,507
PinoleCity18,543
MoragaTown16,322
ClaytonCity10,842

Unincorporated communities (CDPs)

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

CommunityPopulationAlso in
Bay Point24,231
El Sobrante16,294
Discovery Bay14,911
Alamo14,488
Blackhawk10,137
Rodeo8,976
Contra Costa Centre6,893
Camino Tassajara5,831
Saranap5,662
Kensington5,179
Tara Hills4,840
Pacheco4,325
San Miguel3,967
North Richmond3,855
Rollingwood3,627
Vine Hill3,540
Crockett3,372
Reliez Valley3,173
East Richmond Heights3,109
Bayview2,751
Mountain View2,418
Knightsen2,264
Montalvin Manor2,063
Bethel Island1,864
Byron1,837
Diablo1,232
Castle Hill1,026
Norris Canyon1,014
Acalanes Ridge1,006
Alhambra Valley979
North Gate806
Shell Ridge746
Clyde653
Port Costa296

ZIP codes in Contra Costa County

49 ZIP codes reach into Contra Costa County. ZIP codes ignore county lines, so some also cover a neighboring county.

Population of Contra Costa County, 2020–2025

Contra Costa County grew by 4,035 people (+0.4%) between April 2020 and July 2025: 14,796 more births than deaths and a net loss of 11,964 people from migration.

Year (July 1)Population
20201,166,249
20211,164,370
20221,160,163
20231,161,953
20241,169,534
20251,170,070

Neighboring counties

Printable Contra Costa 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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