How many people live in San Mateo County, CA?
Updated Apr. 6, 2026Refreshed annually
In 2024, there were about 742,900 people living in San Mateo County, CA. That makes San Mateo County the 15th-most populous county in California. It is home to 1.9% of people living in the state.
743K
population of San Mateo County, CA (2024)
1.9%
County share of the California population (2024)
About 742,900 people lived in San Mateo County, CA in 2024.
Population estimates, 2000–2024
What are San Mateo County, CA’s age demographics?
About 139,800 San Mateo County, CA residents are aged 65 and older in 2024. That represents 18.8% of its population. For comparison, the age group represents 16.6% of California’s population and 18% in the US overall.
Another 140,200 San Mateo County residents, or 18.9% of the population, were children under 18. For comparison, the age group represents 21.4% of California’s population and 21.6% in the US overall.
A lower share of San Mateo County, CA's population is aged under 18 than the US as a whole.
Population estimates by age group, (2024)
What are San Mateo County, CA’s racial and ethnic demographics?
Non-Hispanic Asian residents make up 33% of the San Mateo County, CA population, higher than the national share of 6.5%. San Mateo County, CA also has a larger share of people identifying as Hispanic (25%) than the US overall (20%).
In contrast, San Mateo County’s non-Hispanic white population accounts for 34.6%, below the 57.5% nationwide, and the non-Hispanic Black or African American population makes up 2.1% of the county, compared with 12.6% nationally.
Racial and ethnic make up differ based on location. These figures reflect how people identified their race alone (not in combination with other races), and separate out Hispanic or Latino ethnicity, following Census reporting standards.
San Mateo County, CA has a higher share of a non-Hispanic Asian population than California as a whole.
Population estimates by race and ethnicity, (2024)
The largest city or town in San Mateo County, CA is San Mateo with about 103,000 residents in 2024.
Cities and towns in San Mateo County, CA ranked by population
Population (2024), includes only portions within county
| City or town | Population | |
|---|---|---|
| 1. | San Mateo | 103,006 |
| 2. | Daly City | 101,418 |
| 3. | Redwood City | 82,982 |
| 4. | South San Francisco | 64,660 |
| 5. | San Bruno | 42,035 |
| 6. | Pacifica | 37,056 |
| 7. | Menlo Park | 33,040 |
| 8. | Foster City | 32,657 |
| 9. | Burlingame | 30,885 |
| 10. | San Carlos | 29,403 |
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Methodology
USAFacts standardizes data, in areas such as time and demographics, to make it easier to understand and compare.
The analysis was generated with the help of AI and reviewed by USAFacts for accuracy.
Page sources
USAFacts endeavors to share the most up-to-date information available. We sourced the data on this page directly from government agencies; however, the intervals at which agencies publish updated data vary.
