San Mateo County, California Population 2026
Updated April 2026 · US Census ACS 2023 5-Year Estimates · 15th-largest in California
The population of San Mateo County, California is 745,100 as of the 2023 American Community Survey, making it the 15th-largest county in California. The median household income is $156,000, the median home value is $1,494,500, and the median age is 40.6.
The population of San Mateo County has grown 3.2% since 2010 (719,948 → 742,893), a +0.22% annualized rate.
745,100
Population
+0.22%
Annual growth
1661
People / sq mi
$156,000
Median Income
$1,494,500
Median Home Value
San Mateo County covers 449 sq mi of land at 1660.9 people per square mile.
About San Mateo County, CA
Housing cost is the defining feature of San Mateo County: the median home is valued at $1,494,500. San Mateo County is a county in California with a population of 745,100. It ranks #15 among counties in California by population.
Earnings sit at the high end: a median household income of $156,000, above the US median of $78,538. Very few residents live in poverty — 3.8%, below the national 12.4%. Home prices are steep, with the typical property valued at $1,494,500, with typical rent around $2,893.
San Mateo County is among the best-educated US counties: 53.1% of adults 25 and older hold a bachelor’s degree, above the national 35.0%. Working from home is common here: 21.9% of workers do so, above the national 14.0%, and the average commute runs about 27 minutes each way.
High housing values reframe the income picture in San Mateo County — even solid earnings stretch less against home prices and rents at this level.
San Mateo County Population History (2010-2024)
The county of San Mateo County had a population of 719,948 in 2010 and 742,893 in 2024, a 3.2% growth over 14 years. The peak was 768,658 in 2017. Average annual growth rate: 0.23%.
742,893
Population (2024)
719,948
Population (2010)
768,658
Peak (2017)
0.23%
Avg Annual Growth
| Year | Population |
|---|---|
| 2010 | 719,948 |
| 2011 | 728,945 |
| 2012 | 739,700 |
| 2013 | 749,131 |
| 2014 | 757,653 |
| 2015 | 765,479 |
| 2016 | 767,928 |
| 2017 | 768,658 |
| 2018 | 768,410 |
| 2019 | 764,810 |
| 2020 | 762,727 |
| 2021 | 739,330 |
| 2022 | 732,485 |
| 2023 | 734,267 |
| 2024 | 742,893 |
Race & Ethnicity
| White | 40.7% |
| Black or African American | 2.2% |
| Asian | 0.0% |
| Hispanic or Latino (any race) | 2.2% |
| Two or More Races | 0.1% |
Age & Sex
40.6
Median Age
50.2%
Female
49.8%
Male
17.3%
Age 65+
Age Distribution
Children (under 15): 16.3% · Seniors (65+): 17.3%
Income & Poverty
| Median household income | $156,000+$59,666 vs state |
| Mean household income | $226,660 |
| Per-capita income | $81,980 |
| Poverty rate | 3.8%-4.6% vs state |
| Unemployment rate | 3.0% |
| Employment-to-population | 64.2% |
Top Industries by Employment
The largest employment sector in San Mateo County is finance & real estate, accounting for 21.5% of workers.
How residents commute
6.4%
Drive alone
2.3%
Carpool
57.6%
Public transit
21.9%
Work from home
27.3 min
Avg commute
Housing
$1,494,500+$799,100 vs state
Median home value
$2,893
Median rent
59.1%
Homeownership rate
285,558
Total housing units
92.6%
Occupied
7.4%
Vacant
40.9%
Renter-occupied
Social & access
96.1%
With health insurance
97.5%
With broadband internet
14.6%
Foreign-born
3.1%
Veterans (18+)
9.0%
With a disability
54.7%
Speak language other than English at home
Education
90.3%
High School+
53.1%
Bachelor's+
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County rankings
Common questions about San Mateo County, CA
Frequently Asked Questions
San Mateo County, California has a population of 745,100 according to the US Census Bureau's 2023 American Community Survey 5-year estimates, making it the 15th-largest county in California. Population density is 1661 people per square mile.
The population of San Mateo County has grown 3.2% since 2010 (719,948 → 742,893), a +0.22% annualized rate.
The median household income in San Mateo County, California is $156,000, with mean (average) household income of $226,660 and per-capita income of $81,980. 3.8% of residents live below the federal poverty level.
In San Mateo County, the largest racial and ethnic groups are White (40.7%), Black or African American (2.2%), Hispanic or Latino (2.2%). Figures are from the US Census Bureau's 2023 ACS 5-year estimates and reflect self-reported responses.
The median age in San Mateo County, California is 40.6 years. Residents are 50.2% female and 49.8% male.
The median home value in San Mateo County is $1,494,500 and median monthly rent is $2,893. 59.1% of occupied housing units are owner-occupied. The county has 285,558 total housing units, 7.4% of which are vacant.
The largest employment sector in San Mateo County, California is finance, insurance, and real estate, employing 21.5% of workers. The unemployment rate is 3.0%.
Los Angeles is among the largest cities associated with San Mateo County, California, with a population of 3,857,897.
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Data from the American Community Survey (ACS) 5-Year estimates.
Source: U.S. Census Bureau ACS, 2026.