Marin County, California population
County or county equivalent · Official geographic code 06041
· Annual resident population estimate
U.S. Census Bureau · Population Estimates Program · Vintage 2025
-2,010 residents (-0.79%) since July 1, 2024.
Marin County had an estimated 253,694 residents on July 1, 2025, the 26th most populous of 58 counties and county equivalents in California. Its population fell 0.79% between July 2024 and July 2025, compared with -0.02% for California and +0.52% for the United States.
- Population change, 2020–2025
- -7,643July 1 to July 1 · -2.92%
- Land-area density, 2025
- 487.7People per square mile · 2025 land area
- Rank in California, 2025
- 26 of 58291 of 3,144 nationally
Marin County population history
Open historical explorerThe six July 1 estimates in the table belong to one consistent Vintage 2025 series. The Census Bureau revises earlier years when it releases a new vintage; a figure from an older publication may differ from the value below.
Vintage 2025, July 1, 2020–2025 Intercensal, 2010–2020
The highest observed population in this annual series was 261,337 in 2020. This is a peak within 2020–2025 coverage, not an all-time record.
| Reference date | Population | Annual change |
|---|---|---|
| July 1, 2020 | 261,337 | — |
| July 1, 2021 | 259,349 | -1,988 |
| July 1, 2022 | 257,038 | -2,311 |
| July 1, 2023 | 255,443 | -1,595 |
| July 1, 2024 | 255,704 | +261 |
| July 1, 2025 | 253,694 | -2,010 |
Why is the April 2020 estimates base different from a census count?
The PEP estimates base here is 262,312 residents on April 1, 2020. It incorporates the Census Bureau’s corrections and geographic revisions and serves as the starting point for this annual series. It is not labeled an original 2020 census count. The chart starts at July 1, 2020, so its five-year change uses two July observations. Read about measurement types.
Marin County population by year, 2010–2020
From the April 2010 estimates base to the April 2020 census count, Marin County gained 9,896 residents (+3.9%). These Census Bureau intercensal estimates use 2020 boundaries and were released in November 2024.
| Date | Population | Annual change |
|---|---|---|
| April 1, 2010 · estimates base | 252,425 | — |
| July 1, 2010 | 253,015 | — |
| July 1, 2011 | 255,926 | +2,911 |
| July 1, 2012 | 257,071 | +1,145 |
| July 1, 2013 | 259,862 | +2,791 |
| July 1, 2014 | 262,261 | +2,399 |
| July 1, 2015 | 263,269 | +1,008 |
| July 1, 2016 | 263,455 | +186 |
| July 1, 2017 | 263,145 | -310 |
| July 1, 2018 | 263,698 | +553 |
| July 1, 2019 | 263,129 | -569 |
| April 1, 2020 · census count | 262,321 | — |
The April 2020 census count (262,321) and the Vintage 2025 April 2020 base (262,312) differ by 9. The gap comes from boundary changes and the Census Bureau’s revised 2020 base, not population change, so measure growth within one series. Source and download
Growth and density
Between July 1, 2020 and July 1, 2025, Marin County lost 7,643 residents, a 2.92% decrease. The annualized change over these five elapsed years was -0.59%. Annualized change is a summary of the interval; it does not imply that the population changed at that rate in every year.
The 2025 Gazetteer reports 520.14 square miles of land. Dividing the July 1, 2025 population by that compatible land area gives 487.7 people per square mile. Water area is excluded. Density depends on geographic boundaries. It describes this entire geography, rather than a typical neighborhood or built-up area.
Calculations use unrounded source values. Population counts are displayed as integers, percentages to two decimals and density to one decimal. Calculation methods · Growth calculator
Components of population change
The published components cover July 1, 2024 through June 30, 2025. Natural change equals births minus deaths. Net migration is arrivals minus departures; it does not establish why people moved.
| Component | People |
|---|---|
| Births | 2,172 |
| Deaths | 2,144 |
| Natural change | +28 |
| Net domestic migration | -2,764 |
| Net international migration | +738 |
| Residual | -12 |
| Total population change | -2,010 |
Reconciliation: natural change + net domestic migration + net international migration + residual = -2,010. Births and deaths are already included in natural change and must not be added again. Source: co-est2025-alldata.csv; Vintage 2025.
How Marin County compares
Growth rates below use the same Vintage 2025 series for every row, so they can be compared directly. A county’s rate reflects all of its towns and unincorporated areas together.
| Geography | Population · 2025 | Growth · 2024–25 | Growth · 2020–25 |
|---|---|---|---|
| Marin County | 253,694 | -0.79% | -2.92% |
| California | 39,355,309 | -0.02% | -0.44% |
| United States | 341,784,857 | +0.52% | +3.08% |
Marin County demographics: age, race and income
The median age in Marin County is 47.4 years, compared with 37.9 in California. 61.1% of adults 25 and older hold a bachelor’s degree or higher, and the median household income is $149,091. About 8.3% of residents live below the poverty level, and 19.6% were born outside the United States.
These are American Community Survey 5-year estimates for 2020–2024. They describe the 60 months ending in December 2024, come from a sample survey with the margins of error shown, and are separate from the July 1, 2025 population estimate above.
| Characteristic | Marin County | Margin | California | U.S. |
|---|---|---|---|---|
| Age and sex | ||||
| Median age | 47.4 | ±0.3 | 37.9 | 38.9 |
| Under 18 years | 19.4% | ±0.4 | 22.0% | 22.0% |
| 65 years and over | 23.8% | ±0.6 | 15.7% | 17.2% |
| Female | 50.8% | ±0.1 | 50.1% | 50.5% |
| Race and Hispanic origin | ||||
| Hispanic or Latino (any race) | 19.5% | ±<0.1 | 40.2% | 19.3% |
| White alone, not Hispanic | 65.1% | ±0.4 | 33.8% | 57.4% |
| Black alone, not Hispanic | 2.1% | ±0.2 | 5.2% | 11.9% |
| Asian alone, not Hispanic | 6.1% | ±0.3 | 15.3% | 5.9% |
| American Indian and Alaska Native, not Hispanic | 0.1% | ±<0.1 | 0.3% | 0.5% |
| Native Hawaiian and Pacific Islander, not Hispanic | 0.2% * | ±0.1 | 0.3% | 0.2% |
| Some other race, not Hispanic | 1.2% | ±0.3 | 0.6% | 0.6% |
| Two or more races, not Hispanic | 5.9% | ±0.4 | 4.4% | 4.3% |
| Born outside the United States | 19.6% | ±0.7 | 27.0% | 14.1% |
| Households and education | ||||
| Households | 103,018 | ±725 | 13,548,091 | 129,227,496 |
| Average household size | 2.44 | ±0.02 | 2.84 | 2.53 |
| Bachelor’s degree or higher, age 25+ | 61.1% | ±1.3 | 37.1% | 35.7% |
| Income and poverty | ||||
| Median household income | $149,091 | ±$4,474 | $99,122 | $80,734 |
| Below the poverty level | 8.3% | ±0.7 | 12.0% | 12.5% |
Margins are 90% margins of error. * The margin is large relative to the estimate (coefficient of variation above 30%); treat it as approximate. Percentages are computed from published Summary File counts with Census Bureau margin formulas. ACS survey population: 257,969; 2024 boundaries. Source and download
Geographic context
County equivalents include parishes, boroughs, census areas, independent cities, DC and Connecticut planning regions where represented by Census. The places listed below are whole-city observations and can extend into other counties. Summing them will not reproduce this county total.
| Place | Population · 2025 | Change · 2024–25 | Growth · 2024–25 | People / sq. mi. |
|---|---|---|---|---|
| San RafaelCalifornia · Incorporated place · 0668364 | 59,410 | -409 | -0.68% | 3,581.7 |
| NovatoCalifornia · Incorporated place · 0652582 | 51,947 | -233 | -0.45% | 1,898.0 |
| Mill ValleyCalifornia · Incorporated place · 0647710 | 13,799 | -76 | -0.55% | 2,884.1 |
| LarkspurCalifornia · Incorporated place · 0640438 | 12,620 | -117 | -0.92% | 4,207.8 |
| San AnselmoCalifornia · Incorporated place · 0664434 | 12,555 | -52 | -0.41% | 4,693.1 |
| Corte MaderaCalifornia · Incorporated place · 0616462 | 9,929 | -56 | -0.56% | 3,144.2 |
| TiburonCalifornia · Incorporated place · 0678666 | 8,881 | -43 | -0.48% | 1,978.2 |
| FairfaxCalifornia · Incorporated place · 0623168 | 7,417 | -42 | -0.56% | 3,328.8 |
| SausalitoCalifornia · Incorporated place · 0670364 | 7,019 | -44 | -0.62% | 3,979.1 |
| RossCalifornia · Incorporated place · 0662980 | 2,304 | +1 | +0.04% | 1,478.5 |
Showing 10 of 11 related records.
California population · State city directory · City proper versus county versus metro
California counties and county equivalents with nearby population ranks
Neighboring 2025 population ranks within California. Similar population does not imply similar density, boundaries or demographics.
| Place | Population · 2025 | Change · 2024–25 | Growth · 2024–25 | People / sq. mi. |
|---|---|---|---|---|
| San Luis Obispo County | 282,367 | +214 | +0.08% | 85.5 |
| Santa Cruz County | 258,852 | -2,565 | -0.98% | 581.6 |
| Yolo County | 224,410 | +1,150 | +0.52% | 221.5 |
| Butte County | 209,211 | +625 | +0.30% | 127.8 |
Source, citation and downloads
U.S. Census Bureau, Population Estimates Program, Vintage 2025, co-est2025-alldata.csv, variable POPESTIMATE2025; Marin County, California, geographic code 06041; resident population 253,694 on July 1, 2025; boundaries January 1, 2025. https://www2.census.gov/programs-surveys/popest/datasets/2020-2025/counties/totals/co-est2025-alldata.csv. Retrieved September 30, 2026. US Population Data snapshot pep-2025-r1, transformation 1.
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