San Mateo County, California

San Mateo County, officially the County of San Mateo, is a county located in the U.S. state of California. As of the 2010 census, the population was 718,451. The county seat is Redwood City.
San Mateo County is included in the San Francisco–Oakland–Berkeley, CA Metropolitan Statistical Area, and is part of the San Francisco Bay Area, the nine counties bordering San Francisco Bay. It covers most of the San Francisco Peninsula. San Francisco International Airport is located at the northern end of the county, and Silicon Valley begins at the southern end. 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 upon the division of San Francisco County, one of the state's 18 original counties established at California statehood in 1850. 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 state 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. The consolidated city-county of San Francisco was formed by a bill introduced by Horace Hawes and signed by the governor on. San Mateo County was officially organized on under a bill introduced by Senator T.G. Phelps. The 1857 bill defined the southern boundary of San Mateo County as following the south branch of San Francisquito Creek to its source in the Santa Cruz Mountains and thence due west to the Pacific Ocean, and named Redwood City as the county seat. San Mateo County then annexed part of northern Santa Cruz County in March 1868, including Pescadero and Pigeon Point.
Although the formation bill named Redwood City the county seat, a May 1856 election marked by "unblushing frauds perpetuated on an unorganized and wholly unprotected community by thugs and ballot stuffers from San Francisco" named Belmont the county seat. The election results were declared illegal and the county government was moved to Redwood City, with land being donated from the original Pulgas Grant for the county government on. Redwood City's status as county seat was upheld in two successive elections in May 1861 and, defeating San Mateo and Belmont. Another election in May 1874 named San Mateo the county seat, but the state supreme court overturned that election on and the county seat has remained at Redwood City ever since.
San Mateo County bears the Spanish name for Saint Matthew. As a place name, San Mateo appears as early as 1776 in the diaries of Anza and Font. Several local geographic features were also designated San Mateo on early maps including variously: a settlement, an arroyo, a headland jutting into the Pacific, and a large land holding. Until about 1850, the name appeared as San Matheo.

Japanese Americans in San Mateo

The Japanese first arrived in San Mateo county and were part of a group guided by Ambassador Tomomi Iwakura back in 1872. There were a number of all male Japanese students who came to San Mateo to learn English and many other helpful skills to bring back to Japan. These students were also some of the first Japanese to join American students in the Belmont school for boys. These students had to work for their housing and food before classes and in the evenings. Many of the first Japanese immigrants were able to find jobs as gardeners and landscapers In San Mateo. Most of them had good educational background from their homelands, but their lack of knowing the English language made it difficult for them to find other jobs in the beginning.


According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. It is the third-smallest county in California by land area. 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.


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.
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.

Flora and fauna

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.
In May 2014, a California condor was spotted near Pescadero, a coastal community south of San Francisco—it was the first California condor spotted in San Mateo County since 1904. The Condor, tagged with the number "597," and also known as "Lupine", is one of 439 condors living in the wild or captivity in California, Baja California and Arizona. The three-year-old female flew more than north from Pinnacles National Park, in San Benito County, on May 30, and landed on a private, forested property near Pescadero, on the San Mateo County Coast, where it was photographed by a motion-activated wildlife camera. Harold Heath, Professor Emeritus, of Stanford University was responsible for the 1904 sighting, west of the University campus.
Puma, also known as mountain lions, roam the county.
Tule elk were native to San Mateo County and among the "favored foods" of the Ohlone people based on ethnohistoric and archeological evidence there. The discovery of two elk specimens made news in 1962, one a royal elk from a peat bog excavated in Pacifica's historic Laguna Alta, and now in the Museum of Vertebrate Zoology collection. These may date from the time of Spanish settlement. Laguna Alta lay just south of the Interstate 280 and Skyline Boulevard intersection, east of Mussel Rock. The California Academy of Sciences also has an elk skull fragment collected one mile inland from the mouth of Purisima Creek in 1951. Additional coastal elk remains dating from the Middle and Late Periods in Northern California were found in at least five more late Holocene archeological sites in San Mateo County: SMA-115, SMA-118, SMA-244, SMA-97 and SMA-218. On the eastern side of the San Francisco Peninsula, elk remains were also unearthed at multiple archaeological sites along San Francisquito Creek.

National protected areas

See for trail descriptions.
The County of San Mateo Parks Department operates 22 parks, trails, and historic sites spread throughout the county:
1Coyote PointSan Mateo/Burlingame
2Crystal SpringsBurlingame
3Devil's SlidePacifica/Montara
4EdgewoodRedwood City
5Fitzgerald1969Moss Beach
6FloodMenlo Park
7Friendship<Redwood City
9Junipero SerraSan Bruno
10Memorial1924Loma Mar
11Mirada SurfEl Granada
12Moss Beach2014Moss Beach
13Pescadero CreekLoma Mar
14Pillar PointMoss Beach
15QuarryEl Granada
16Sam McDonaldLoma Mar
17San Bruno MountainBrisbane
18San Pedro ValleyPacifica
19Sanchez AdobePacifica
20Tunitas Creek BeachHalf Moon Bay
21Woodside StoreWoodside

Prior to the rebuilding of the San Mateo Bridge that began in 1996, the county had also operated Werder Pier for fishermen; it had been the western segment of the original 1929 vertical-lift bridge.
In addition to the county-operated parks, San Mateo County voters created the Midpeninsula Regional Open Space District in 1972, administered by the Peninsula Open Space Trust, which owns several protected spaces within San Mateo County. San Mateo County protected spaces administered by POST include:
As of 2012, San Mateo County had one of the largest Tongan communities outside of Tonga, with an estimated 13,000 Tongan Americans.


Places by population, race, and income


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 White, 20,436 African American, 3,306 Native American, 178,118 Asian, 10,317 Pacific Islander, 84,529 from other races, and 38,210 from two or more races. Hispanic or Latino of any race were 182,502 persons ; 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.


As of the census of 2009, there were 714,936 people, 258,648 households, and 174,582 families residing in the county. The population density was 2,753/sq mi. There were 284,471 housing units at an average density of 789/sq mi. 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.


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 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.
San Mateo County is split between California's 14th and 18th congressional districts, represented by and, respectively.
In the California State Assembly, San Mateo County is split between three legislative districts:
  • ,
  • , and
  • .
In the California State Senate, San Mateo is split between the 11th and 13th districts, represented by and, respectively.


Voter registration

Cities by population and voter registration


Historically, San Mateo County was a Republican stronghold in presidential elections. From 1892 until 1988, the only Democrats to carry San Mateo County were Woodrow Wilson, Franklin Roosevelt, Lyndon Johnson, and Hubert Humphrey. Like virtually all counties in the Bay Area, San Mateo today 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.
The California Secretary of State, as of February 2019, reports that San Mateo County has 404,958 registered voters. Of those voters, 202,341 are registered Democratic, 60,045 are registered Republican, 15,834 are registered with other political parties, and 126,738 declined to state a political party preference. Every city, town, and unincorporated area of San Mateo County has more registered Democrats than Republicans.
On November 4, 2008 San Mateo County voted 61.8% against Proposition 8, which amended the California Constitution to ban same-sex marriages.
201618.43% 57,92975.67% 237,8825.91% 18,573
201225.46% 72,75672.13% 206,0852.41% 6,879
200824.75% 75,05773.47% 222,8261.78% 5,409
200429.25% 83,31569.48% 197,9221.27% 3,620
200030.95% 80,29664.29% 166,7574.76% 12,346
199629.22% 73,50860.55% 152,30410.22% 25,720
199227.15% 75,08053.97% 149,23218.88% 52,196
198842.94% 109,26155.74% 141,8591.32% 3,360
198451.87% 135,18546.91% 122,2681.22% 3,178
198048.82% 116,49136.60% 87,33514.59% 34,811
197650.63% 117,33844.40% 102,8964.97% 11,507
197252.82% 135,37742.82% 109,7454.36% 11,175
196843.72% 98,65447.20% 106,5199.08% 20,495
196435.55% 77,91664.32% 140,9780.14% 297
196051.70% 104,57048.04% 97,1540.26% 528
195661.04% 100,04938.83% 63,6370.13% 217
195263.61% 92,27935.95% 52,1490.45% 651
194856.69% 48,90939.66% 34,2153.65% 3,148
194449.15% 33,59050.62% 34,5940.23% 158
194046.60% 26,53952.38% 29,8311.02% 581
193633.09% 13,65065.67% 27,0871.24% 511
193239.68% 13,44256.36% 19,0943.96% 1,343
192858.87% 14,36039.99% 9,7551.14% 277
192455.27% 8,1265.24% 77139.48% 5,805
192070.52% 7,20519.16% 1,95810.32% 1,054
191650.01% 5,20743.08% 4,4856.91% 719
19120.10% 746.47% 3,24653.42% 3,732
190862.91% 2,86528.85% 1,3148.23% 375
190468.45% 2,14627.15% 8514.40% 138
190063.00% 1,64535.01% 9141.99% 52
189661.10% 1,60737.53% 9871.37% 36
189250.56% 1,08847.40% 1,0202.05% 44


The following table includes the number of incidents reported and the rate per 1,000 persons for each type of offense.

Cities by population and crime rates


A July 2013 Wall Street Journal article identified the Facebook initial public offering 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 50% higher than the next highest county, New York County, which came in at $2,107 a week, or roughly $110,000 a year."
Additionally, San Mateo County hosts the headquarters of Oracle Corporation, Visa Inc, Sony Interactive Entertainment, Electronic Arts, YouTube, Genentech, and Gilead Sciences, as well as a hub of venture capital firms in Menlo Park and several other technology related companies.
In 2016, Peninsula Clean Energy began providing electricity to 20 percent of residential customers, all municipalities, and all small- to mid-size businesses in the county, as a Community Choice Aggregation program, an alternative to Pacific Gas and Electric.


The people of San Mateo county may use the services of San Mateo County Libraries along with 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. The San Mateo County Board of Education oversees early education, special education, and the court and community schools program in the county, as well as serves as an appeal board for the adjudication of expulsion appeals, interdistrict attendance appeals, and Charter 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. The center's mascot is the banana slug, a large yellow gastropod. The school uses songs from the famous Banana Slug String Band.


Major highways

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 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.


is geographically located in San Mateo County, but it is owned and operated 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.

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.

Notable structures

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


  • Belmont
  • Brisbane
  • Burlingame
  • Daly City
  • East Palo Alto
  • Foster City
  • Half Moon Bay
  • Menlo Park
  • Millbrae
  • Pacifica
  • Redwood City
  • San Bruno
  • San Carlos
  • San Mateo
  • South San Francisco


  • Atherton
  • Colma
  • Hillsborough
  • Portola Valley
  • Woodside

    Census-designated places

  • Broadmoor
  • El Granada
  • Emerald Lake Hills
  • Highlands-Baywood Park
  • Ladera
  • La Honda
  • Loma Mar
  • Montara
  • Moss Beach
  • North Fair Oaks
  • Pescadero
  • West Menlo Park

    Unincorporated communities

  • Burlingame Hills
  • Devonshire
  • Kings Mountain
  • Los Trancos Woods
  • Menlo Oaks
  • Palomar Park
  • Princeton-by-the-Sea
  • San Gregorio
  • Sky Londa

    Population ranking

The population ranking of the following table is based on the 2010 census of San Mateo County.
county seat
RankCity/Town/etc.Municipal typePopulation
1Daly CityCity101,123
2San MateoCity97,207
3 Redwood CityCity76,815
4South San FranciscoCity63,632
5San BrunoCity41,114
7Menlo ParkCity32,026
8Foster CityCity30,567
10San CarlosCity28,406
11East Palo AltoCity28,155
14North Fair OaksCDP14,687
15Half Moon BayCity11,324
18El GranadaCDP5,467
20Portola ValleyTown4,353
22Emerald Lake HillsCDP4,278
24Highlands-Baywood ParkCDP4,027
25West Menlo ParkCDP3,659
26Moss BeachCDP3,103
30La HondaCDP928
32Loma MarCDP113 Text is available under the Creative Commons Attribution-ShareAlike License.