County Maps US

Contra Costa County, California

A county in California, ranked 9 of 58 by population.

CountyFIPS 06013

Within California
Contra Costa County, highlighted, with the areas around it. Boundaries generalised from the 2025 Census cartographic boundary file; neighbour fills carry no data. The dot marks Martinez, the county seat, located via the 2025 Census Gazetteer.

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Population
1,170,070
+3,821 (+0.3%) since 2020
Land area
716.9
square miles. A further 10.8% of the total area is water
Population density
1,632
people per square mile, computed rather than published
County seat
Martinez
Seat of county government.
Established
1850
175 years ago
Largest city
Concord city
Population 123,261.

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; Wikidata (CC0), Wikidata. Retrieved 30 August 2026.

Satellite view

Aerial imagery of Contra Costa County with its boundary drawn on top. A map shows you the shape; this shows you what is inside it, and which side of the line a place falls on.

Aerial view of Contra Costa County, California from the USGS National Map, with its boundary outlined
Imagery: USGS National Map, USGS Imagery Only, public domain, requested from USGS by your browser when you reach this point on the page, at 800 by 471 pixels. The boundary is the 2025 Census cartographic boundary file, reprojected to Web Mercator to match the imagery. You can also open the USGS National Map viewer.

Where Contra Costa County ranks

Position among the 58 counties of California, and among all 3,144 US counties and county-equivalents. Computed from the figures on this page.

MeasureValueIn CaliforniaNationally
Population1,170,0709th of 5841st of 3,144
Land area716.9 sq mi51st of 581,261st of 3,144
Population density1,632 per sq mi7th of 5897th of 3,144
Median household income$127,2296th of 5836th of 3,143

Full data for Contra Costa County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population1,170,070Vintage 2025 Population Estimates
Population in 20201,166,249Vintage 2025 Population Estimates
2020 estimates base?1,166,035Vintage 2025 Population Estimates
Land area716.9 sq mi2025 Gazetteer Files
Water area87.0 sq mi2025 Gazetteer Files
Total area803.9 sq mi2025 Gazetteer Files
Population density?1,632 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$127,229American Community Survey 2020-2024 5-Year Estimates
Median home value$866,800American Community Survey 2020-2024 5-Year Estimates
Median age40.5American Community Survey 2020-2024 5-Year Estimates
Households414,417American Community Survey 2020-2024 5-Year Estimates
Housing units429,260American Community Survey 2020-2024 5-Year Estimates

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026. Population density is computed here, not published: it divides the Vintage 2025 population estimate by the 2025 Gazetteer land area, which are two different Census products. Retrieved 30 August 2026.

How the population changed

The Census Bureau publishes the components behind an estimate, not just the total. For the year to July 2025:

Births minus deaths
+2,868
11,195 births, 8,327 deaths
Net migration
-2,390
More people moved out than moved in.

Source: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026. Retrieved 30 August 2026.

The 7 areas bordering Contra Costa County

Ordered by the length of the border actually shared, which the Census Bureau publishes in its county adjacency file and which no other county reference presents.

Bordering areaStateShared borderPopulation
Alameda CountyCalifornia56 mi1,636,630
San Joaquin CountyCalifornia35 mi823,815
Solano CountyCalifornia29 mi455,376
Sacramento CountyCalifornia21 mi1,618,460
Marin CountyCalifornia12 mi253,694
San Francisco CountyCalifornia4.5 mi826,079
Sonoma CountyCaliforniaa single point486,444

Source: US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. Retrieved 30 August 2026.

Side by side

All 58 counties of California

Open the interactive California county map, or jump straight to any of them.

Data on this page last rebuilt 30 August 2026. How these figures are produced.