San Mateo County Demographics

A map of San Mateo County's Population by Race

Race	2024 Pop	2020 Pop	2024 %	2020 %
White	257,595	275,902	34.7%	36.1%
Asian	230,413	227,783	31.0%	29.8%
Hispanic	184,940	191,386	24.9%	25.0%
Multiracial	38,779	38,969	5.2%	5.1%
Native American/Other	15,904	15,701	2.1%	2.1%
Black	14,709	14,701	2.0%	1.9%

San Mateo County, California has an estimated population of 742,340, a slight decrease from the 764,442 recorded in the 2020 Census. The population is 34.7% White, 31.0% Asian, 24.9% Hispanic, 5.2% Multiracial, 2.1% Native American/Other, and 2.0% Black. This demographic dot map shows the population of San Mateo County, with one dot drawn for each person counted by the Census, color-coded by race.

San Mateo is about as racially diverse as it was in the 2020 Census. It is more diverse than California overall. Demographers use a diversity index to measure the probability that two randomly selected individuals belong to different racial or ethnic groups. In San Mateo County, that probability was 71.5% in 2020 and 71.8% in the most recent ACS estimates.

San Mateo County is ranked the 15th most populous county in California, out of 58 counties. San Mateo County was ranked the 15th most populous county in the 2020 Census.

San Mateo County's White Population

257,595 residents of San Mateo County, or 34.7% of the population, identify as White. The share of White residents in San Mateo County is comparable to the share in California overall, where 33.8% of the population is White. San Mateo County ranks 41st statewide in terms of White residents as a share of the population, out of 58 counties.

Since the 2020 Census, San Mateo County's White population has declined by an estimated 6.6%. White residents' share of San Mateo County's population has decreased from 36.1% to 34.7%.

San Mateo County is more White than neighboring Alameda County (27.4% White), and Santa Clara County (27.2% White). San Mateo County is less White than neighboring San Francisco County (36.8% White), Santa Cruz County (53.9% White), and Contra Costa County (38.1% White).

San Mateo County's Black Population

14,709 residents of San Mateo County, or 2.0% of the population, identify as Black. The share of Black residents in San Mateo County is slightly lower than in California overall, where 5.2% of the population is Black. San Mateo County ranks 26th statewide in terms of Black residents as a share of the population, out of 58 counties.

Since the 2020 Census, San Mateo County's Black population has remained roughly the same. Black residents' share of San Mateo County's population has remained roughly unchanged at 2.0%.

San Mateo County is more Black than neighboring Santa Cruz County (0.7% Black). San Mateo County is less Black than neighboring San Francisco County (4.7% Black), Alameda County (9.3% Black), Contra Costa County (7.9% Black), and Santa Clara County (2.2% Black).

San Mateo County's Asian Population

230,413 residents of San Mateo County, or 31.0% of the population, identify as Asian. The share of Asian residents in San Mateo County is significantly higher than in California overall, where 15.3% of the population is Asian. San Mateo County ranks 4th statewide in terms of Asian residents as a share of the population, out of 58 counties.

Since the 2020 Census, San Mateo County's Asian population has grown by an estimated 1.2%. Asian residents' share of San Mateo County's population has increased from 29.8% to 31.0%.

San Mateo County is more Asian than neighboring Santa Cruz County (4.7% Asian), and Contra Costa County (18.6% Asian). San Mateo County is less Asian than neighboring San Francisco County (34.9% Asian), Alameda County (32.7% Asian), and Santa Clara County (40.3% Asian).

San Mateo County's Hispanic Population

184,940 residents of San Mateo County, or 24.9% of the population, identify as Hispanic. The share of Hispanic residents in San Mateo County is significantly lower than in California overall, where 40.2% of the population is Hispanic. San Mateo County ranks 33rd statewide in terms of Hispanic residents as a share of the population, out of 58 counties.

Since the 2020 Census, San Mateo County's Hispanic population has declined by an estimated 3.4%. Hispanic residents' share of San Mateo County's population has remained roughly unchanged at 24.9%.

San Mateo County is more Hispanic than neighboring San Francisco County (16.2% Hispanic), and Alameda County (23.4% Hispanic). San Mateo County is less Hispanic than neighboring Santa Cruz County (35.2% Hispanic), Contra Costa County (27.6% Hispanic), and Santa Clara County (25% Hispanic).

San Mateo County's Native American/Other Population

15,904 residents of San Mateo County, or 2.1% of the population, identify as American Indian/Alaska Native/Native Hawaiian/Pacific Islander/Other. The share of Native American/Other residents in San Mateo County is comparable to the share in California overall, where 1.2% of the population is Native American/Other. San Mateo County ranks 22nd statewide in terms of Native American/Other residents as a share of the population, out of 58 counties.

Since the 2020 Census, San Mateo County's Native American/Other population has grown by an estimated 1.3%. Native American/Other residents' share of San Mateo County's population has remained roughly unchanged at 2.1%.

San Mateo County is more Native American/Other than neighboring San Francisco County (1.3% Native American/Other), Alameda County (1.6% Native American/Other), Santa Cruz County (1% Native American/Other), Contra Costa County (1.4% Native American/Other), and Santa Clara County (1.1% Native American/Other).

San Mateo County's Multiracial Population

38,779 residents of San Mateo County, or 5.2% of the population, identify as Multiracial. The share of Multiracial residents in San Mateo County is comparable to the share in California overall, where 4.4% of the population is Multiracial. San Mateo County ranks 29th statewide in terms of Multiracial residents as a share of the population, out of 58 counties.

Since the 2020 Census, San Mateo County's Multiracial population has remained roughly the same. Multiracial residents' share of San Mateo County's population has remained roughly unchanged at 5.2%.

San Mateo County is more Multiracial than neighboring Santa Cruz County (4.5% Multiracial), and Santa Clara County (4.2% Multiracial). San Mateo County is less Multiracial than neighboring San Francisco County (6.1% Multiracial), Alameda County (5.6% Multiracial), and Contra Costa County (6.3% Multiracial).

Sources: Most recent population estimates are from the 2020-2024 American Community Survey 5-Year Estimates. 2020 population counts and map data are from 2020 Census State Redistricting Data. Geographic data are from Census TIGER/Line Shapefiles.