The San Francisco Peninsula is a

peninsula A peninsula is a landform that extends from a mainland and is only connected to land on one side. Peninsulas exist on each continent. The largest peninsula in the world is the Arabian Peninsula. Etymology The word ''peninsula'' derives , . T ...

in the

San Francisco Bay Area The San Francisco Bay Area, commonly known as the Bay Area, is a List of regions of California, region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose, California, S ...

that separates

San Francisco Bay San Francisco Bay (Chochenyo language, Chochenyo: 'ommu) is a large tidal estuary in the United States, U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the cities of San Francisco, California, San ...

from the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

. On its northern tip is the City and County of San Francisco. Its southern base is Los Altos and Mountain View, in

Santa Clara County Santa Clara County, officially the County of Santa Clara, is the sixth-most populous county in the U.S. state of California, with a population of 1,936,259 as of the 2020 census. Santa Clara County and neighboring San Benito County form the ...

, south of

Palo Alto Palo Alto ( ; Spanish language, Spanish for ) is a charter city in northwestern Santa Clara County, California, United States, in the San Francisco Bay Area, named after a Sequoia sempervirens, coastal redwood tree known as El Palo Alto. Th ...

and north of Sunnyvale. Most of the Peninsula is occupied by

San Mateo County San Mateo County ( ), officially the County of San Mateo, is a county (United States), county located in the U.S. state of California. As of the 2020 United States census, the population was 764,442. Redwood City, California, Redwood City is th ...

, between San Francisco and Santa Clara counties, and including the cities and towns of Atherton, Belmont,

Brisbane Brisbane ( ; ) is the List of Australian capital cities, capital and largest city of the States and territories of Australia, state of Queensland and the list of cities in Australia by population, third-most populous city in Australia, with a ...

, Burlingame, Colma, Daly City, East Palo Alto, El Granada, Foster City,

Half Moon Bay Half Moon Bay is a coastal city in San Mateo County, California, San Mateo County, California, United States, approximately south of San Francisco. Its population was 11,795 2020 United States census, 2020 census. Immediately north of Half Mo ...

, Hillsborough, La Honda, Loma Mar, Los Altos, Los Altos Hills, Menlo Park, Millbrae, Mountain View, Pacifica,

, Pescadero, Portola Valley, Redwood City, Redwood Shores, San Bruno, San Carlos, San Mateo, South San Francisco, West Menlo Park and Woodside. Whereas the term ''peninsula'' in a geographical sense technically refers to the entire San Francisco Peninsula, in local jargon, "The Peninsula" does not include the city of San Francisco.

History

In 1795, Governor Diego de Borica gave José Darío Argüello a Spanish land grant known as Rancho de las Pulgas. This rancho was the largest grant on the peninsula consisting of . As a local geographic term, the area referred to as "the Peninsula" is distinct from that denoted by "the City", and refers to the portion south of San Francisco. The appellation may date to the period prior to 1856, when the City of San Francisco and the County of San Francisco were separate entities, the latter then coextensive with contemporary San Mateo County and San Francisco City-County. The City-County owns several disjunct properties along the whole of the Peninsula (mostly water pumping stations connected to the Hetch Hetchy Valley on which San Francisco has a permanent leasehold) – thus, most of the larger communities in San Mateo County are ''de facto'' suburbs of San Francisco, with the neighboring communities of Pacifica, Daly City, Broadmoor, Colma, South San Francisco, Half Moon Bay, San Bruno, and Brisbane being immediate suburbs. The remaining suburban area of the Peninsula is on the east side of the

Santa Cruz Mountains The Santa Cruz Mountains ( Mutsun Ohlone: Mak-sah-re-jah, "Sharp Ridged Mountain of the Eagle" or "People of the Eagle Mountain") are a mountain range in central and Northern California, United States, constituting a part of the Pacific Coast R ...

, along

; the west and south-central portions of the Peninsula are mostly rural, unincorporated, and unorganized areas. A substantial portion of

Silicon Valley Silicon Valley is a region in Northern California that is a global center for high technology and innovation. Located in the southern part of the San Francisco Bay Area, it corresponds roughly to the geographical area of the Santa Clara Valley ...

is located on the peninsula. In Silicon Valley are the headquarters of some of the largest tech companies in the world, such as Google, Yahoo, Facebook, and Apple. Since 2010, droughts and

wildfires A wildfire, forest fire, or a bushfire is an unplanned and uncontrolled fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identified as a ...

have increased in frequency and become less seasonal and more year-round, further straining the region's water security.

Geography and transportation

Along the center line of the Peninsula is the northern half of the

, formed by the action of

plate tectonics Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

along the

San Andreas Fault The San Andreas Fault is a continental Fault (geology)#Strike-slip faults, right-lateral strike-slip transform fault that extends roughly through the U.S. state of California. It forms part of the tectonics, tectonic boundary between the Paci ...

. In the middle of the Peninsula along the fault is the Crystal Springs Reservoir. Just north of the Crystal Springs reservoir is San Andreas Lake, after which the

geologic fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

was originally named. The east side of the peninsula is a densely populated and largely urban and suburban area that includes portions of Silicon Valley. It forms a commuter area between San Francisco to the north and San Jose to the south.

Roads

Interstate 80 Interstate 80 (I-80) is an east–west transcontinental freeway that crosses the United States from San Francisco, California, to Teaneck, New Jersey, in the New York metropolitan area. The highway was designated in 1956 as one of the ori ...

* Interstate 280 * Interstate 380 *

U.S. Route 101 U.S. Route 101, or U.S. Highway 101 (US 101), is a major north–south highway that traverses the states of California, Oregon, and Washington on the West Coast of the United States. It is part of the United States Numbered Highway Syst ...

State Route 1 * California 9

State Route 9 * California 35

State Route 35 * California 82

State Route 82 * California 84

State Route 84 * California 85

State Route 85 * California 92

State Route 92 * California 109

State Route 109 * California 114

State Route 114 * California 237

State Route 237 The bridges in the Peninsula include the Dumbarton Bridge, the

Golden Gate Bridge The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the strait connecting San Francisco Bay and the Pacific Ocean in California, United States. The structure links San Francisco—the northern tip of the San Francisco Peni ...

, the San Francisco - Oakland Bay Bridge, and the San Mateo–Hayward Bridge. A number of major thoroughfares run north-south: El Camino Real ( SR 82) and US 101 on the east side along the bay, Interstate 280 down the center, Skyline Boulevard ( SR 35) along the crest of the

, and SR 1 on the west along the Pacific, and SR 85 which forms the southern end of the Peninsula.

Transit

Caltrain Caltrain (reporting mark JPBX) is a commuter rail line in California, serving the San Francisco Peninsula and Santa Clara Valley (Silicon Valley). The southern terminus is in San Jose, California, San Jose at the Tamien station with weekday r ...

is the primary passenger rail transit in the peninsula, serving much of the eastern urbanized areas of the peninsula between Mountain View (which also connects to VTA light rail) and San Francisco's 4th and King Street station. In addition, the peninsula has access to

Bay Area Rapid Transit Bay Area Rapid Transit (BART) is a rapid transit system serving the San Francisco Bay Area in California. BART serves 50 stations along six routes and of track, including eBART, a spur line running to Antioch, and Oakland Airport Connecto ...

(BART) northward of Millbrae, connecting San Mateo County and San Francisco to the

East Bay The East Bay is the eastern region of the San Francisco Bay Area and includes cities along the eastern shores of San Francisco Bay and San Pablo Bay. The region has grown to include inland communities in Alameda and Contra Costa counties. Wi ...

through a route over and under Daly City, Glen Park, San Francisco's Mission district, and through part of Market Street subway. Bus service is predominantly provided by SamTrans and the SFMTA's Muni buses, which primarily run in San Mateo and San Francisco counties respectively. In addition, southward of Palo Alto, the

Santa Clara Valley Transportation Authority The Santa Clara Valley Transportation Authority, more commonly known simply as the Valley Transportation Authority (VTA), is a Special district (United States), special district responsible for public transit services, Congestion management agen ...

operates buses to other parts of Santa Clara County. Most of the peninsula's bus transit to the

and North Bay flowing through San Francisco, as neither

AC Transit AC Transit is the main Public transport bus service, bus transit operator in the East Bay region of the San Francisco Bay Area, California. AC Transit is the third largest bus operator in California, serving the western portions of Alameda and C ...

nor Golden Gate Transit, the primary transit operators for the East and North Bay respectively, serve the peninsula south of San Francisco.

Airports

The peninsula's largest commercial airport is

San Francisco International Airport San Francisco International Airport is the primary international airport for the San Francisco Bay Area in the U.S. state of California. Owned and operated by the City and County of San Francisco, the airport has a San Francisco mailing ...

, itself connected to US 101 and BART and accessible to Caltrain (via a BART connection at Milbrae station). San Jose International Airport, is the next largest airport in the region serving and might be a more viable option for the southern peninsula. The airport is connected to US 101 and there is a single connector bus, VTA Line 60, that links to Caltrain (at Santa Clara Transit Center) and to eastern lines of BART (Milpitas).

Oakland International Airport Oakland International Airport is an international airport in Oakland, California, United States. The airport is located south of downtown Oakland and east of San Francisco, serving the East Bay of the San Francisco Bay Area. The airport is ...

, located in the

, is the smallest of the three and is also accessible directly via BART.

Environmental features

The San Francisco Peninsula contains a variety of habitats including estuarine, marine, oak woodland, redwood forest, coastal scrub and oak

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach th ...

. There are numerous species of wildlife present, especially along the

estuarine

shoreline A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

San Bruno Mountain San Bruno Mountain is a fault block, fault-block Horst (geology), horst in northern San Mateo County, California. Rising to a quarter-mile high peak directly out of San Francisco Bay, it also includes a smaller ridge in San Francisco. Viewed f ...

, Fitzgerald Marine Reserve and the

forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...

s on the Montara Mountain block. The area is home to several endangered species including the San Francisco garter snake, the

Mission blue butterfly The Mission blue (''Icaricia icarioides missionensis'') is a blue or lycaenid butterfly subspecies native to the San Francisco Bay Area of the United States. The butterfly has been declared as endangered by the US federal government. It is a s ...

and the San Bruno elfin butterfly, all of which are endemic to

. The

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

California clapper rail is also found on the shores of

, in the cities of Belmont and San Mateo. Although

tule elk The tule elk (''Cervus canadensis nannodes'') is a subspecies of elk found only in California, ranging from the grasslands and marshlands of the Central Valley to the grassy hills on the coast. The subspecies name derives from the tule (), ...

, an elk subspecies found only in California, were historically native to the San Francisco Peninsula, they were hunted to extinction by 1850. Expansion of Diablo Range elk to western

, and San Mateo and Santa Cruz Counties has been blocked by U.S. Highway 101 in Coyote Valley south of

San Jose, California San Jose, officially the City of San José ( ; ), is a cultural, commercial, and political center within Silicon Valley and the San Francisco Bay Area. With a city population of 997,368 and a metropolitan area population of 1.95 million, it is ...

. A number of noteworthy parks and nature preserves are found on the San Francisco Peninsula, including: * Edgewood Park, San Mateo County *

Golden Gate National Recreation Area The Golden Gate National Recreation Area (GGNRA) is a U.S. National Recreation Area protecting of ecologically and historically significant landscapes surrounding the San Francisco Bay Area. Much of the park is land formerly used by the Unite ...

—several units are located on the Peninsula * Midpeninsula Regional Open Space District—several preserves * Shoreline Park, Mountain View, Santa Clara County

Notable structures

There are a number of well-known structures and complexes on the San Francisco Peninsula: * Bay Meadows Racecourse, San Mateo (demolished in 2008) * Carolands Mansion, Hillsborough * Cow Palace, Daly City * Crocker Mansion, Hillsborough * Crystal Springs Reservoir, west of Interstate 280 * CuriOdyssey museum, San Mateo * Dakin Building, Brisbane *

Meta Platforms Meta Platforms, Inc. is an American multinational technology company headquartered in Menlo Park, California. Meta owns and operates several prominent social media platforms and communication services, including Facebook, Instagram, Threads ...

, world headquarters, Menlo Park * Filoli mansion and gardens, Woodside * Frenchman's Tower, Palo Alto * Google Inc., World Headquarters, Mountain View * " The Flintstone House", east side of Interstate 280
* Notre Dame de Namur University, Belmont, with Ralston Hall *

Oracle An oracle is a person or thing considered to provide insight, wise counsel or prophetic predictions, most notably including precognition of the future, inspired by deities. If done through occultic means, it is a form of divination. Descript ...

World Headquarters, Redwood Shores (aka the "Emerald City") * Pulgas Water Temple, Woodside *

* Sanchez Adobe Park, Pacifica *

Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...

campus, Palo Alto

References

External links

* {{Coord, 37, 35, 00, N, 122, 24, 04, W, source:GNIS_scale:500000, display=title Peninsulas of California Landforms of the San Francisco Bay Area Geography of San Francisco Geography of San Mateo County, California Geography of Santa Clara County, California Regions of California *