Data as of October 18, 2026 · refreshed automatically from the official California voter file
Sonoma County, CA has 320,392 active registered voters — 18.2% Republican, 55.3% Democratic, and 18.4% with no party affiliation, as of October 2026.
Party registration
Most reliable-voting precincts
| # | Precinct | Active voters | Supervoters | Supervoter % |
|---|---|---|---|---|
| 1 | 0100122 | 702 | 605 | 86.18% |
| 2 | 0110087 | 915 | 787 | 86.01% |
| 3 | 0500263 | 773 | 660 | 85.38% |
| 4 | 0110002 | 1,293 | 1,092 | 84.45% |
| 5 | 0100264 | 698 | 588 | 84.24% |
| 6 | 0110089 | 981 | 815 | 83.08% |
| 7 | 0110052 | 650 | 530 | 81.54% |
| 8 | 0110050 | 851 | 692 | 81.32% |
| 9 | 0500003 | 420 | 336 | 80.0% |
| 10 | 0180006 | 729 | 575 | 78.88% |
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 Sonoma County voted for president
Election results are public records.
Sonoma County at a glance.
Sonoma County had an estimated 485,375 residents in July 2024, the 17th most populous of California's 58 counties, down 0.7% since the 2020 census. Of those, 395,970 are 18 or older, the voting-age population, and 22.8% are 65 or older. Its 320,392 active registered voters equal about 80.9% of that voting-age population.
It covers 1,575 square miles of land (308 people per square mile), and 27.3% of residents live outside any incorporated city or town. The largest cities and towns are Santa Rosa (177,524), Petaluma (59,393), Rohnert Park (44,894), Windsor (25,846) and Healdsburg (11,231). The American Community Survey (2020-2024) puts it at a median age of 42.9, a median household income of $104,674, 38.5% of adults 25 and older holding a bachelor's degree or higher and 62.6% of occupied homes owned by the people living in them.
In 2024, 251,426 votes were cast for president, about 63.5% of the voting-age population; the Democratic ticket took 71.4% and the Republican ticket 25.2%. The two-party margin moved from D+49.6 in 2008 to D+46.2 in 2024.
- Population (2024 estimate)
- 485,375
- Population (2020 census base)
- 488,862
- Voting-age population (18+)
- 395,970
- Active voters per 100 adults
- 80.9
- Residents 65 and older
- 22.8%
- People per square mile
- 308
- Living outside incorporated places
- 27.3%
- Land area
- 1,575 sq mi
- Median age
- 42.9
- Median household income
- $104,674
- Adults 25+ with a bachelor's degree
- 38.5%
- Owner-occupied homes
- 62.6%
Largest cities and towns
- Santa Rosa 177,524
- Petaluma 59,393
- Rohnert Park 44,894
- Windsor 25,846
- Healdsburg 11,231
Presidential vote, 2008–2024
| Year | Democratic | Republican | Margin | Votes cast |
|---|---|---|---|---|
| 2024 | 71.4% | 25.2% | D+46.2 | 251,426 |
| 2020 | 74.5% | 23.0% | D+51.5 | 268,252 |
| 2016 | 70.7% | 22.8% | D+47.9 | 164,060 |
| 2012 | 70.8% | 26.0% | D+44.8 | 175,738 |
| 2008 | 73.6% | 24.0% | D+49.6 | 229,351 |
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.
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