Demographics of San Mateo County, California

San Mateo County, California had 743,568 people on July 1, 2025, by the Census Bureau’s estimate: −19,071 since July 2020. Age, income, poverty, housing and origin below come from the American Community Survey, averaged over 2020–2024, each with its margin of error.

San Mateo County, in four figures

743,568
Population: July 1, 2025, Vintage 2025 estimate.; −2.5%
Change since July 2020: −19,071 people.; 40.9 ±0.2
Median age: ACS 2020–⁠2024.; $158,855 ±$2,851
Median household income: ACS 2020–⁠2024, in 2024 dollars.

Population, year by year

July 1 estimates from the Census Bureau’s Vintage 2025. Each year's change is births less deaths, net moves from abroad and net moves from elsewhere in the country, with the Bureau's small residual. The 2020 row's components run 3 months, from the April census to July 1.

San Mateo County, California's population shrank 2.5% from July 2020 to July 2025, against +3.1% nationally

The July 1 estimate of San Mateo County, California's resident population and the nation's, each year of the Census Bureau's Vintage 2025, as a share of its July 2020 level (= 100).

U.S. Census Bureau — Census Bureau population estimates — counties and Puerto Rico municipios, with components of change

About this chart

The figures

San Mateo County, California's population shrank 2.5% from July 2020 to July 2025, against +3.1% nationally. The July 1 estimate of San Mateo County, California's resident population and the nation's, each year of the Census Bureau's Vintage 2025, as a share of its July 2020 level (= 100).
July 1	Population	Index	United States
2020	762,639	100.0	100.0
2021	739,463	97.0	100.2
2022	732,245	96.0	100.7
2023	733,949	96.2	101.6
2024	740,627	97.1	102.5
2025	743,568	97.5	103.1

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Population of San Mateo County, California on July 1 of each year, Vintage 2025
July 1	Population	Change	Births less deaths	From abroad	From elsewhere in the country
2020	762,639	−1,869	+638	+101	−2,526
2021	739,463	−23,176	+2,234	+1,715	−25,429
2022	732,245	−7,218	+2,632	+7,632	−18,103
2023	733,949	+1,704	+2,123	+10,102	−10,604
2024	740,627	+6,678	+2,306	+10,320	−5,955
2025	743,568	+2,941	+2,279	+4,737	−4,110

Age, 2020–2024

The median age is 40.9 ±0.2: for men 39.6 ±0.2 and for women 42.2 ±0.2. Shares are of everyone the survey counts, in the Bureau’s sex-by-age table (B01001).

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People in San Mateo County by age, ACS 2020–2024
Age	People	Share	California	United States
Under 5	37,891 ±145	5.1% ±<0.1	5.5% ±<0.1	5.6% ±<0.1
5 to 17	107,204 ±1,653	14.4% ±0.2	16.5% ±<0.1	16.3% ±<0.1
18 to 24	54,440 ±1,390	7.3% ±0.2	9.1% ±<0.1	9.1% ±<0.1
25 to 44	214,469 ±1,961	28.9% ±0.3	28.7% ±<0.1	26.9% ±<0.1
45 to 64	196,094 ±1,877	26.4% ±0.3	24.6% ±<0.1	24.8% ±<0.1
65 and over	132,242 ±2,067	17.8% ±0.3	15.7% ±<0.1	17.2% ±<0.1

Income and poverty, 2020–2024

Median household income is $158,855 ±$2,851, and income per person $84,288 ±$1,230, in 2024 dollars. The median is $99,122 ±$310 in California and $80,734 ±$166 in the United States.

Households by income

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Households in San Mateo County by income, ACS 2020–2024
Household income	Households	Share	California	United States
Under $25,000	18,645 ±1,077	7.1% ±0.4	12.5% ±0.1	14.6% ±<0.1
$25,000 to $49,999	22,264 ±1,241	8.4% ±0.5	13.3% ±0.1	16.7% ±<0.1
$50,000 to $74,999	23,074 ±1,245	8.7% ±0.5	13.0% ±0.1	15.5% ±<0.1
$75,000 to $99,999	22,305 ±1,226	8.4% ±0.5	11.6% ±0.1	12.6% ±<0.1
$100,000 to $149,999	39,915 ±1,511	15.1% ±0.6	17.8% ±0.1	17.5% ±<0.1
$150,000 to $199,999	32,583 ±1,459	12.3% ±0.5	11.3% ±0.1	9.6% ±<0.1
$200,000 or more	105,633 ±2,178	39.9% ±0.8	20.5% ±0.1	13.4% ±0.1

Poverty by age

The poverty rate is the share of people whose family income is below the federal threshold for their family’s size, of everyone for whom the Bureau determines it (B17020).

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Poverty rate in San Mateo County by age, ACS 2020–2024
Age	Below poverty	Rate	California	United States
All ages	49,359 ±2,960	6.7% ±0.4	12.0% ±0.1	12.5% ±0.1
Under 18	8,829 ±1,021	6.2% ±0.7	15.0% ±0.1	16.1% ±0.1
18 to 59	25,374 ±1,676	6.1% ±0.4	11.0% ±0.1	11.6% ±0.1
60 and over	15,156 ±1,093	8.6% ±0.6	11.5% ±0.1	11.0% ±<0.1

Housing, 2020–2024

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Housing in San Mateo County, ACS 2020–2024
Measure	San Mateo County	California	United States
Housing units	287,184 ±144	14,644,735 ±1,665	143,775,355 ±10,234
Occupied	92.1% ±0.4	92.5% ±0.1	89.9% ±0.1
Vacant	7.9% ±0.4	7.5% ±0.1	10.1% ±0.1
Owner occupied	58.5% ±0.7	55.9% ±0.3	65.2% ±0.3
Renter occupied	41.5% ±0.7	44.1% ±0.2	34.8% ±0.1
Median home value	$1,559,600 ±$16,159	$734,700 ±$1,307	$332,700 ±$236
Median gross rent	$2,922 ±$40	$2,036 ±$5	$1,413 ±$2
Median year built	1966 ±1	1976 ±1	1980 ±1

Occupied and vacant are shares of all housing units; owner and renter occupied are shares of occupied units. Value and rent are medians in 2024 dollars.

Origin and place of birth, 2020–2024

Hispanic or Latino origin is not a race in the Census Bureau’s tables. Here the people of Hispanic origin, of any race, are one row, and everyone else is counted by race alone (B03002), so the rows add to the whole.

Hispanic origin and race

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People in San Mateo County by Hispanic origin and race, ACS 2020–2024
Origin	People	Share	California	United States
Hispanic or Latino	184,940 ±0	24.9% ±<0.1	40.2% ±<0.1	19.3% ±<0.1
White alone, not Hispanic	257,595 ±1,125	34.7% ±0.2	33.8% ±<0.1	57.4% ±<0.1
Black alone, not Hispanic	14,709 ±760	2.0% ±0.1	5.2% ±<0.1	11.9% ±<0.1
Asian alone, not Hispanic	230,413 ±1,815	31.0% ±0.2	15.3% ±<0.1	5.9% ±<0.1
American Indian and Alaska Native alone, not Hispanic	861 ±181	0.1% ±<0.1	0.3% ±<0.1	0.5% ±<0.1
Native Hawaiian and Other Pacific Islander alone, not Hispanic	8,031 ±553	1.1% ±0.1	0.3% ±<0.1	0.2% ±<0.1
Some other race alone, not Hispanic	7,012 ±1,202	0.9% ±0.2	0.6% ±<0.1	0.6% ±<0.1
Two or more races, not Hispanic	38,779 ±2,077	5.2% ±0.3	4.4% ±<0.1	4.3% ±<0.1

Place of birth and citizenship

“Born a citizen outside the states” counts people born in Puerto Rico, the island areas, or abroad to American parents. Naturalized citizens and those who are not citizens together make up the people born abroad (B05002).

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People in San Mateo County by place of birth and citizenship, ACS 2020–2024
Born	People	Share	California	United States
Born in the state	358,865 ±4,054	48.3% ±0.5	56.5% ±0.1	57.3% ±<0.1
Born in another state	104,215 ±2,563	14.0% ±0.3	15.0% ±0.1	26.9% ±<0.1
Born a citizen outside the states	14,002 ±1,074	1.9% ±0.1	1.5% ±<0.1	1.7% ±<0.1
Born abroad	265,258 ±4,228	35.7% ±0.6	27.0% ±0.1	14.1% ±<0.1
Naturalized citizens	154,706 ±3,307	20.8% ±0.4	14.7% ±0.1	7.4% ±<0.1
Not citizens	110,552 ±3,370	14.9% ±0.5	12.3% ±0.1	6.8% ±<0.1

San Mateo County among the counties of California

15th of 58 by population, July 2025. Every one is listed on the California page.

Counties of California near San Mateo County in population, July 2025
County	July 2025	Change since 2020
Fresno County	1,035,456	+2.6%
Kern County	927,068	+2.3%
Ventura County	830,851	−1.5%
San Francisco County	826,079	−5.6%
San Joaquin County	823,815	+5.5%
San Mateo County	743,568	−2.5%
Stanislaus County	557,719	+0.7%
Sonoma County	486,444	−0.4%
Tulare County	485,146	+2.4%
Solano County	455,376	+0.5%
Placer County	442,081	+8.9%

Elsewhere on the site

Sources

Census Bureau population estimates — counties and Puerto Rico municipios, with components of change — U.S. Census Bureau · U.S. Government work · retrieved September 25, 2026
American Community Survey 5-year estimates — table-based Summary File · U.S. Government work

Data retrieved September 25, 2026