San Mateo county

County of San Mateo
Official seal of County of San Mateo

Location in the state of California
Country  United States
State  California
Region/Metro area San Francisco Bay Area
Incorporated 1856
County seat Redwood City
Largest city Daly City
 • Total 741.01 sq mi (1,919.2 km2)
 • Land 449.07 sq mi (1,163.1 km2)
 • Water 291.95 sq mi (756.1 km2)
Population (2010)
 • Total 718,451
 • Density 1,599.6/sq mi (617.6/km2)
Time zone Pacific Standard Time (UTC-8)
 • Summer (DST) Pacific Daylight Time (UTC-7)

San Mateo County (/ˌsæn məˈt./ ; Spanish for "Saint Matthew") is a county located in the San Francisco Bay Area of the U.S. state of California. It covers most of the San Francisco Peninsula just south of San Francisco, and north of Santa Clara County. San Francisco International Airport is located at the northern end of the county, and Silicon Valley begins at the southern end. As of 2010 the population was 718,451. The county seat is Redwood City. It is ethnically diverse, and affluent. The county's built-up areas are mostly suburban with some areas being very urban, and are home to several corporate campuses.


San Mateo County was formed in 1856 after San Francisco County, one of state's 18 original counties since California's statehood in 1850, was split apart. Until 1856, San Francisco's city limits extended west to Divisadero Street and Castro Street, and south to 20th Street. In response to the lawlessness and vigilantism that escalated rapidly between 1855 and 1856, the California government decided to divide the county. A straight line was then drawn across the tip of the San Francisco Peninsula just north of San Bruno Mountain. Everything south of the line became the new San Mateo County while everything north of the line became the new consolidated City and County of San Francisco, to date the only consolidated city-county in California.[1][2] San Mateo County then annexed part of northern Santa Cruz County in 1868.[1]

San Mateo county bears the Spanish name for Saint Matthew. As a place name, San Mateo appears as early as 1776 and several local geographic features were also designated San Mateo on early maps including variously: a settlement, an arroyo, a headland jutting into the Pacific (Point Montara), and a large land holding (Rancho San Mateo). Until about 1850, the name appeared as San Matheo.


According to the 2000 census, the county has a total area of 741.01 square miles (1,919.2 km2), of which 449.07 square miles (1,163.1 km2) (or 60.60%) is land and 291.95 square miles (756.1 km2) (or 39.40%) is water.[3] A number of bayside watercourses drain the eastern part of the county including San Bruno Creek and Colma Creek. Streams draining the western county include Frenchmans Creek, Pilarcitos Creek, Naples Creek, Arroyo de en Medio, and Denniston Creek. These streams originate along the northern spur of the Santa Cruz Mountains that run through the county. The northern and north-east parts of the county are very heavy densely populated with largely urban and suburban areas, with many of its cities as edge-cities for the Bay Area, whilst the deep south and the west central parts of the county are less heavy densely populated with more rural environment and coastal beaches areas.

Incorporated cities

Unincorporated communities

Adjacent counties

National protected areas

Marine protected areas

Transportation infrastructure

Major highways

Public transportation

SamTrans (San Mateo County Transit District) provides local bus service within San Mateo County. Local and commuter bus routes also operate into San Francisco.

Caltrain, the commuter rail system, traverses the county from north to south, running alongside the Highway 101 corridor for most of the way. Bay Area Rapid Transit (BART) trains serve San Francisco International Airport and the northern portion of the county, terminating at Millbrae.

Caltrain, BART, and SamTrans converge at the Millbrae Intermodal station.


San Francisco International Airport is geographically located in San Mateo County, but it is owned by the City and County of San Francisco.

San Mateo County does own two general aviation airports: Half Moon Bay Airport and San Carlos Airport. [4]

Marine transport

The only deepwater port in South San Francisco Bay is the Port of Redwood City, situated along Redwood Creek, originally created as a lumber embarcadero in 1850. The San Mateo Harbor Harbor District manages the Pillar Point Harbor and Oyster Point Marina. Ferry connections connect Oyster Point to Jack London Square in Oakland and the Alameda Ferry Terminal in Alameda.


San Mateo County had one of the largest Tongan communities outside of Tonga, with an estimated 13,000 Tongan Americans.[5]


Places by population, race, and income


Historical population
Census Pop.
Est. 2012739,3112.9%
U.S. Decennial Census[14]
2012 Estimate[15]

The 2010 United States Census reported that San Mateo County had a population of 718,451. The racial makeup of San Mateo County was 383,535 (53.4%) White, 20,436 (2.8%) African American, 3,306 (0.5%) Native American, 178,118 (24.8%) Asian (9.8% Filipino, 9.0% Chinese, 1.9% Indian, 1.2% Japanese, 0.8% Korean, 0.5% Vietnamese, 0.3% Burmese, 0.1% Pakistani), 10,317 (1.4%) Pacific Islander, 84,529 (11.8%) from other races, and 38,210 (5.3%) from two or more races. Hispanic or Latino of any race were 182,502 persons (25.4%); 15.7% of San Mateo County is Mexican, 2.7% Salvadoran, 1.2% Guatemalan, 1.2% Nicaraguan, 0.7% Peruvian, 0.6% Puerto Rican, 0.2% Colombian, and 0.2% Cuban.[16]


As of the census of 2009,[18] there were 714,936 people, 258,648 households, and 174,582 families residing in the county. The population density was 2,753/sq mi (825/km²). There were 284,471 housing units at an average density of 789/sq mi (432/km²). 7.4% were of Italian, 7.1% Irish, 7.0% German and 5.3% English ancestry according to Census 2000. 46.9% spoke English, 28.4% Spanish, 6.2% Tagalog, 4.0% Chinese or Mandarin and 1.1% Cantonese, and other language 4.2%, as their first language from estimate census 2009.

There were 258,648 households out of which 30% had children under the age of 18, 48.6% were married couples living together, 14.7% had a female householder with no husband present, and 41.7% were non-families. 31.5% of all households were made up of individuals and 6.2% had someone living alone who was 65 years of age or older. The average household size was 3.79 and the average family size was 4.44.

In the county, the population was spread out with 28.6% under the age of 18, 15.9% from 18 to 24, 25.8% from 25 to 44, 21% from 45 to 64, and 9.7% who were 65 years of age or older. The median age was 31 years. For every 100 females there were 97.8 males. For every 100 females age 18 and over, there were 95.1 males.

The median income for a household in the county was $69,306, and the median income for a family was $77,737. Males had a median income of $48,342 versus $45,383 for females. The per capita income for the county was $36,045. About 6.42% of families and 9.51% of the population were below the poverty line, including 10.01% of those under age 18 and 8.52% of those age 65 or over.


Voter registration statistics

Cities by population and voter registration


San Mateo County vote
by party in presidential elections
Year GOP DEM Others
2012 25.5% 72,756 72.3% 206,087 2.2% 6,299
2008 24.8% 75,006 73.6% 222,767 1.6% 4,963
2004 29.3% 83,315 69.5% 197,922 1.3% 3,620
2000 31.0% 80,296 64.3% 166,757 4.8% 12,346
1996 29.2% 73,508 60.6% 152,304 10.2% 25,720
1992 27.2% 75,080 54.0% 149,232 18.9% 52,196
1988 42.9% 109,261 55.7% 141,859 1.3% 3,360
1984 51.9% 135,185 46.9% 122,268 1.2% 3,178
1980 48.8% 116,491 36.6% 87,335 14.6% 34,811
1976 50.6% 117,338 44.4% 102,896 5.0% 11,507
1972 52.8% 135,377 42.8% 109,745 4.4% 11,175
1968 43.7% 98,654 47.2% 106,519 9.1% 20,495
1964 35.6% 77,916 64.3% 140,978 0.1% 297
1960 51.7% 104,570 48.0% 97,154 0.3% 528
1956 61.0% 100,049 38.8% 63,637 0.1% 217
1952 63.6% 92,279 36.0% 52,149 0.5% 651
1948 56.7% 48,909 39.7% 34,215 3.7% 3,148
1944 49.2% 33,590 50.6% 34,594 0.2% 158
1940 46.6% 26,539 52.4% 29,831 1.0% 581
1936 33.1% 13,650 65.7% 27,087 1.2% 511
1932 39.7% 13,442 56.4% 19,094 4.0% 1,343
1928 58.9% 14,360 40.0% 9,755 1.1% 277
1924 55.3% 8,126 5.2% 771 39.5% 5,805
1920 70.5% 7,205 19.2% 1,958 10.3% 1,054

San Mateo County has a five-member Board of Supervisors, representing five geographic districts, elected at-large until November 2012. On November 6, 2012, Measure B passed[20] to amend the San Mateo County Charter so that each member of the Board of Supervisors will cease to be elected by an at-large vote of all the voters in the County, but is instead elected only by the voters of his or her district.[21] The California Secretary of State, as of April 2008, reports that San Mateo County has 357,514 registered voters. Of those voters registered, 179,994 (50.4%) are registered Democratic, 82,189 (23.0%) are registered Republican, 13,648 (3.8%) are registered with other political parties, and 81,683 (22.8%) declined to state a political party preference. With the exceptions of Atherton, Hillsborough, and Woodside, every city, town, and the unincorporated areas of San Mateo County has more registered Democrats than Republicans.

San Mateo is a strongly Democratic county in presidential and congressional elections. The last Republican to win a majority in the county was Ronald Reagan in 1984.

San Mateo County is split between California's 14th and 18th congressional districts, represented by and , respectively.[22]

In the State Assembly, San Mateo is in the 19th, 22nd, and 24th districts, which are held by Democrats Phil Ting, Kevin Mullin, and Rich Gordon, respectively. In the State Senate, San Mateo is in the 8th, 11th, and 13th districts, which are held by Democrats Leland Yee, Mark Leno, and Jerry Hill respectively.

On Nov. 4, 2008 San Mateo County voted 61.8% against Proposition 8, which amended the California Constitution to ban same-sex marriages.[23]

Environmental features

San Mateo County straddles the San Francisco Peninsula, with the Santa Cruz Mountains running its entire length. The county encompasses a variety of habitats including estuarine, marine, oak woodland, redwood forest, coastal scrub and oak savannah. There are numerous species of wildlife present, especially along the San Francisco Bay estuarine shoreline, San Bruno Mountain, Fitzgerald Marine Reserve and the forests on the Montara Mountain block. Several creeks discharge to the San Francisco Bay including San Mateo Creek and Laurel Creek and several coastal streams discharge to the Pacific Ocean such as Frenchmans Creek and San Vicente Creek.

The county is home to several endangered species including the San Francisco garter snake and the San Bruno elfin butterfly, both of which are endemic to San Mateo County. The endangered California clapper rail is also found on the shores of San Francisco Bay, in the cities of Belmont and San Mateo. The endangered wildflower Hickman's potentilla is found near the Pacific Ocean on the lower slopes of Montara Mountain. The endangered wildflowers White-rayed pentachaeta, Pentachaeta bellidiflora, San Mateo Woolly Sunflower, Eriophyllum latilobum, Marin Dwarf Flax, Hesperolinon congestum and the San Mateo Thornmint, Acanthomintha duttonii, are found in the vicinity of the Crystal Springs Reservoir.

Año Nuevo State Marine Conservation Area and Greyhound Rock State Marine Conservation Area are two adjoining marine protected areas off the coast of San Mateo County. Like underwater parks, these marine protected areas help conserve ocean wildlife and marine ecosystems.


The people of San Mateo county may use the services of the Peninsula Library System and its dozens of branches, bookmobile and Library-a-Go-Go machine at the Millbrae BART/Caltrain station.

The county is broken up into several public school districts in addition to the local Catholic diocese and many other private parochial and secular schools.

Some students in San Mateo County's public schools attend outdoor education in La Honda. San Mateo Outdoor Education is a residential school that teaches major concepts of ecology via exploration of forest, pond, garden, tidepool, wetland, and sandy shore habitats.[24] The center's mascot is the banana slug, a large yellow gastropod. The school uses songs from the famous Banana Slug String Band.


Currently Nippon Cargo Airlines has its San Francisco branch on the property of San Francisco International Airport in an unincorporated area in San Mateo County.[25]

Prior to its dissolution, Pacific Air Lines had its corporate headquarters on the grounds of the airport.[26] Prior to its dissolution, Hughes Airwest had its headquarters on the grounds of San Francisco International.[27]

A July 2013 Wall Street Journal article identified the Facebook initial public offering (IPO) as the cause of a change in the U.S.' national economic statistics, as San Mateo County—the home of the company—became the top wage-earning county in the country after the fourth quarter of 2012. The article revealed that the Bureau of Labor Statistics reported that the average weekly wage in the county was US$3,240, which is 107% higher than the previous year: "That’s the equivalent of $168,000 a year, and more than more than 50% higher than the next highest county, New York County (better known as Manhattan), which came in at $2,107 a week, or roughly $110,000 a year."[28]

Notable structures

There are a number of well known structures within San Mateo County:

County trails

See this county page for trail descriptions.

  • Alpine Trail
  • Bog Trail
  • Cañada Trail
  • Crystal Springs Trail
  • Edgewood Trail
  • Ralston Trail
  • San Andreas Trail
  • Sand Hill Trail
  • Sawyer Camp Trail
  • Skyline Trail
  • Sheep Camp Trail
  • Sweeney Ridge Trail
  • Hiking trails in San Mateo County

County parks

State parks

State beaches

See also

San Francisco Bay Area portal



External links

  • County of San Mateo Official Website
  • Visitors Guide from the Visitors Bureau
  • San Mateo County Library – 12 branches throughout the County and a bookmobile
  • Peninsula Library System – serving all of San Mateo County
  • Superior Court Records
  • SamCERA (San Mateo County Employees' Retirement Association
  • Brisbane Baylands Project
  • the Bancroft Library

Coordinates: 37°26′N 122°22′W / 37.44°N 122.36°W / 37.44; -122.36

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