Data as of October 18, 2026 · refreshed automatically from the official California voter file
Contra Costa County, CA has 731,218 active registered voters — 19.1% Republican, 51.6% Democratic, and 22.4% with no party affiliation, as of October 2026.
Party registration
Most reliable-voting precincts
| # | Precinct | Active voters | Supervoters | Supervoter % |
|---|---|---|---|---|
| 1 | WLCR131 | 2,853 | 2,346 | 82.23% |
| 2 | WLCR117 | 2,799 | 2,275 | 81.28% |
| 3 | BREN133 | 2,198 | 1,761 | 80.12% |
| 4 | BREN134 | 780 | 609 | 78.08% |
| 5 | WLCR130 | 2,323 | 1,810 | 77.92% |
| 6 | MART138 | 603 | 466 | 77.28% |
| 7 | WLCR129 | 539 | 409 | 75.88% |
| 8 | KENS101 | 2,238 | 1,678 | 74.98% |
| 9 | WLCR102 | 782 | 585 | 74.81% |
| 10 | ALMO102 | 1,202 | 892 | 74.21% |
Supervoters are active registered voters who cast a ballot in at least 3 of the last 4 November general elections (2018–2024). Percentages are precinct totals from the official state voter file — no individual voter information is shown. Precincts with fewer than 400 active voters are excluded.
How Contra Costa County voted for president
Election results are public records.
Contra Costa County at a glance.
Contra Costa County had an estimated 1,172,607 residents in July 2024, the ninth most populous of California's 58 counties, up 0.6% since the 2020 census. Of those, 921,132 are 18 or older, the voting-age population, and 18.0% are 65 or older. Its 731,218 active registered voters equal about 79.4% of that voting-age population.
It covers 717 square miles of land (1,636 people per square mile), and 15.1% of residents live outside any incorporated city or town. The largest cities and towns are Concord (124,016), Antioch (118,453), Richmond (115,353), San Ramon (85,924) and Pittsburg (77,131). The American Community Survey (2020-2024) puts it at a median age of 40.5, a median household income of $127,229, 45.2% of adults 25 and older holding a bachelor's degree or higher and 68.0% of occupied homes owned by the people living in them.
In 2024, 528,904 votes were cast for president, about 57.4% of the voting-age population; the Democratic ticket took 67.3% and the Republican ticket 29.4%. The two-party margin moved from D+37.8 in 2008 to D+37.9 in 2024.
- Population (2024 estimate)
- 1,172,607
- Population (2020 census base)
- 1,165,983
- Voting-age population (18+)
- 921,132
- Active voters per 100 adults
- 79.4
- Residents 65 and older
- 18.0%
- People per square mile
- 1,636
- Living outside incorporated places
- 15.1%
- Land area
- 717 sq mi
- Median age
- 40.5
- Median household income
- $127,229
- Adults 25+ with a bachelor's degree
- 45.2%
- Owner-occupied homes
- 68.0%
Largest cities and towns
- Concord 124,016
- Antioch 118,453
- Richmond 115,353
- San Ramon 85,924
- Pittsburg 77,131
Presidential vote, 2008–2024
| Year | Democratic | Republican | Margin | Votes cast |
|---|---|---|---|---|
| 2024 | 67.3% | 29.4% | D+37.9 | 528,904 |
| 2020 | 71.6% | 26.3% | D+45.3 | 581,230 |
| 2016 | 68.9% | 25.4% | D+43.5 | 415,972 |
| 2012 | 65.7% | 32.0% | D+33.7 | 351,257 |
| 2008 | 68.0% | 30.2% | D+37.8 | 451,650 |
Sources: U.S. Census Bureau Vintage 2024 population estimates and 2024 Gazetteer; American Community Survey 2020–2024 5-year estimates; certified county presidential returns. Growth, density and turnout are simple arithmetic on those figures.
Running in Contra Costa County?
The voter file is loaded. Create your campaign and start canvassing in minutes.
Start free in Contra Costa CountyAlso see: Motion51 in California · Pricing