San Francisco Bay Area The San Francisco Bay Area , commonly known as the Bay Area , is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California , United States . The region encompasses the major cities and metropolitan areas of San Francisco , Oakland , and San Jose , along with smaller urban and rural areas . The Bay Area ' s nine counties are Alameda , Contra Costa , Marin , Napa , San Francisco , San Mateo , Santa Clara , Solano , and Sonoma . Home to approximately 7 . 15 million people , the nine - county Bay Area contains many cities , towns , airports , and associated regional , state , and national park s , connected by a network of roads , highways , railroads , bridges , tunnels and commuter rail . The combined urban area of San Jose and San Francisco is the largest in Northern California , the second largest in California ( after Los Angeles ) , and the 55th largest urban area in the world . The nine - county definition of the San Francisco Bay Area is not recognized by the United States Census Bureau ; rather , they define a larger 11 - county Combined Statistical Area ( CSA ) designated the San Jose - San Francisco - Oakland , CA CSA , including Santa Cruz and San Benito counties to the south ; counties that do not have a border on the San Francisco Bay but are tied economically to counties that do . As of the 2010 U . S . Census , this larger CSA contains 7 . 46 million people — the sixth - largest CSA in the U . S . The San Francisco Bay Area is renowned for its natural beauty , liberal politics , entrepreneurship , and diversity . The area has high incomes ; it includes the five highest California counties by per capita income and two of the top 25 wealthiest counties in the United States . Sub - regions . East Bay . The eastern side of the bay , consisting of Alameda and Contra Costa counties , is known locally as the East Bay . The East Bay can be loosely divided into two regions , the inner East Bay , which adjoins the Bay shoreline , and the outer East Bay , consisting of inland valleys separated from the inner East Bay by hills and mountains . North Bay . The region north of the Golden Gate Bridge is known locally as the North Bay . This area encompasses Marin County , Sonoma County , Napa County and extends eastward into Solano County . The city of Fairfield , being part of Solano County , is often considered the easternmost city of the North Bay . With few exceptions , this region is quite affluent : Marin County is ranked as the wealthiest in the state . The North Bay is relatively rural compared to the remainder of the Bay Area , with many areas of undeveloped open space , farmland and vineyards . Santa Rosa in Sonoma County is the North Bay ' s largest city , with a population of 167 , 815 and a Metropolitan Statistical Area population of 466 , 891 , making it the fifth largest city in the San Francisco Bay Area . The North Bay is the only section of the Bay Area that is not currently served by a commuter rail service . The lack of transportation services is mainly because of the lack of population mass in the North Bay , and the fact that it is separated completely from the rest of the Bay Area by water , the only access points being the Golden Gate Bridge leading to San Francisco , the Richmond - San Rafael and Carquinez Bridge s leading to Richmond , and the Benicia - Martinez Bridge leading to Martinez . Peninsula . The area from San Francisco to the Silicon Valley , geographically part of the San Francisco Peninsula , is known locally as " The Peninsula " . This area consists of a series of cities and suburban communities in San Mateo County and the northwestern part of Santa Clara County , as well as various towns along the Pacific coast , such as Pacifica and Half Moon Bay . This area is extremely diverse , although it contains significant populations of affluent family households with the exception of East Palo Alto and some parts of Redwood City . Many of the cities and towns had originally been centers of rural life until the post - World War II era when large numbers of middle and upper class Bay Area residents moved in and developed the small villages . Since the 1980s the area has seen a large growth rate of middle and upper - class families who have settled in cities like Palo Alto , Los Altos , Portola Valley , Woodside , and Atherton as part of the technology boom of Silicon Valley . Many of these families are of foreign background and have significantly contributed to the diversity of the area . The Peninsula is also home to what used to be one of the deadliest cities in the United States , East Palo Alto . Peninsula cities include : Atherton , Belmont , Brisbane , Burlingame , Colma , Daly City , East Palo Alto , Foster City , Half Moon Bay , Hillsborough , Los Altos , Los Altos Hills , Menlo Park , Millbrae , Mountain View , Palo Alto , Pacifica , Portola Valley , Redwood City , Redwood Shores , San Bruno , San Carlos , San Mateo , South San Francisco and Woodside . Whereas the term " peninsula " technically refers to the entire geographical San Franciscan Peninsula , in local terms , " The Peninsula " does not include the city of San Francisco itself . San Francisco . San Francisco is surrounded by water on three sides ; the north , east , and west . The city squeezes approximately 805 , 000 people in under , making it the most densely populated major city in North America after New York City . On any given day , there can be as many as 1 million people in the city because of the commuting population and tourism . San Francisco also has the largest commuter population of the Bay Area cities . The limitations of land area , however , make continued population growth challenging , and also has resulted in increased real estate prices . Though San Francisco is located at the tip of the peninsula , when " the peninsula " is discussed , it usually refers to the communities and geographic locations south of the city proper . San Jose and Silicon Valley . The communities at the southern region of the San Francisco Bay Area are primarily located in what is known as Silicon Valley , or the Santa Clara Valley . These include the major city of San Jose , and its suburbs , including the high - tech hubs of Santa Clara , Milpitas , Cupertino , Sunnyvale as well as many other cities like Saratoga , Campbell , Los Gatos and the exurbs of Morgan Hill and Gilroy . Some Peninsula and East Bay towns are sometimes recognized as being in the Santa Clara Valley . Generally , the term South Bay refers to Santa Clara County , but the northwest portion of the county ( Palo Alto , Mountain View , Los Altos and Los Altos Hills ) is considered part of the Peninsula ( even though these cities are in Santa Clara County ) . Silicon Valley was primarily an agricultural center from the time of California ' s founding until World War II . During and after the war , working and middle - class families migrated to the area to settle and work in the burgeoning aerospace and electronics industries . The South Bay Area experienced rapid growth as agriculture was gradually replaced by high - technology . During this period , the Santa Clara Valley gradually became an urbanized metropolitan region . Today , the growth continues , fueled primarily by technology jobs , the weather , and immigrant labor . Urbanization is gradually replacing suburbanization as the population density of the valley increases . This trend has resulted in a huge increase in property values , forcing many middle - class families out of the area or into lower income neighborhoods in older sections of the region . The Santa Clara Valley also came to be known as Silicon Valley , as the area became the premier technology center of the United States . Some notable tech companies headquartered in the South Bay are AMD , Adobe , Intel , Cisco Systems , Hewlett - Packard , Apple , Google , eBay , Facebook and Yahoo ! . Largely a result of the high technology sector , the San Jose - Sunnyvale - Santa Clara , CA Metropolitan Statistical Area has the most millionaires and the most billionaires in the United States per capita . The population of the entire valley is part of the San Jose - Sunnyvale - Santa Clara metropolitan area , which has about 2 million residents . San Jose , the largest city in the Silicon Valley area , is the tenth most populous city in the United States and the most populous city in the Bay Area . San Jose is the oldest city in California and was its first capital . The city prides itself on being an environmentally conscious city . It recycles a greater percentage of its waste than any other large American city . Over the past several decades , the South Bay Area has experienced rapid growth . To limit the effects of urban sprawl , planned communities were laid out to control growth . Urban growth boundaries have been established to protect remaining open space ( primarily in the surrounding hills and southern border ) from development . Most new growth has been urban infill in the form of high density housing to increase density rate . The growth rate has slowed , but the area continues to have steady growth . San Jose is home to many sports teams both amateur and professional , such as the San Jose Sharks of the NHL , and the San Jose Earthquakes of the MLS . The South Bay has a large transportation infrastructure that includes many freeways , VTA bus service and light rail , Amtrak , and commuter rail such as Caltrain . The San Jose International Airport serves air traffic in the South Bay Area and is conveniently located just north of downtown in the center of Silicon Valley . The height of buildings in Downtown is limited ( due to FAA regulations and city ordinance ) because it is situated directly under the flight path . The South Bay is poised to have a more efficient transportation network with the extension of the BART system to San Jose , which would allow elevated / subway travel into San Francisco . San Jose will also be a major stop on the proposed California High - Speed Rail system . Santa Cruz and San Benito . Whether Santa Cruz and San Benito counties are considered part of the San Francisco Bay Area depends on the observer . For example , the regional governments in the San Francisco Bay Area , including the Association of Bay Area Governments , the Metropolitan Transportation Commission , the Bay Area Air Quality Management District ( BAAQMD ) , and the San Francisco Bay Regional Water Quality Control Board ( RWQCB ) include only the nine counties above in their boundaries or membership . ( The BAAQMD includes all of the nine counties except the northern portions of Sonoma and Solano ; the RWQCB includes all of San Francisco and the portions of the other eight counties that drain to San Francisco Bay or to the Pacific Ocean . ) However , the United States Census Bureau defines the San Jose - San Francisco - Oakland Consolidated Statistical Area as an eleven - county region , including the nine counties above plus Santa Cruz and San Benito Counties . Meanwhile , the California State Parks Department defines the Bay Area as including ten counties , including Santa Cruz but excluding San Benito . On the other hand , Santa Cruz and San Benito along with Monterey County are part of a different regional government organization called the Association of Monterey Bay Area Governments . Local media in the San Francisco Bay Area and travel guides often consider these two counties as part of the South Bay subregion , as they are greatly connected geographically , economically , and historically . Economy . In 2011 the San Francisco Bay Area had a GDP of $ 518 . 1 billion , which would rank 20th among countries . The Silicon Valley is located within the southern reaches of the Bay Area . The leading high technology region in the world , Silicon Valley covers San Jose and several cities of South Bay . The Valley is home to many of the industry leaders in technology such as Google , Yahoo ! , Facebook , Cisco , Apple , Oracle , Marvell , Intel , and Hewlett - Packard . Major corporations in San Francisco , San Jose , Oakland , and the surrounding cities help make the region second in the nation in concentration of Fortune 500 companies , after New York . The region ' s northern counties encompass California ' s famous Wine Country , home to hundreds of vineyards and wineries . The Bay Area is a leader in sustainable agriculture , organic farming , and sustainable energy and for being a leading producer of high quality food , wine , and innovation in the culinary arts . California Cuisine was developed primarily in the Bay Area , as was the organic farming movement . The area is renowned for its natural beauty . It is also known as being one of the most expensive regions to live in the country . Oakland , on the east side of the bay , has the fifth largest container shipping port in the United States . The city is also a major rail terminus . Changes in house prices for the Bay Area are publicly tracked on a regular basis using the Case – Shiller index ; the statistic is published by Standard & Poor ' s and is also a component of S & P ' s 10 - city composite index of the value of the U . S . residential real estate market . Demographics . According to the 2010 United States Census , the population was 7 . 15 million in the nine counties bordering the San Francisco Bay . In 2010 the racial makeup of the nine - county Bay Area was 52 . 5 % White including white Hispanic , 6 . 7 % non - Hispanic African American , 0 . 7 % Native American , 23 . 3 % Asian ( 7 . 9 % Chinese , 5 . 1 % Filipino , 3 . 3 % Indian , 2 . 5 % Vietnamese , 1 . 0 % Korean , 0 . 9 % Japanese , 0 . 2 % Pakistani , 0 . 2 % Cambodian , 0 . 2 % Laotian , 0 . 1 % Thai , 0 . 1 % Burmese ) , 0 . 6 % Pacific Islander ( 0 . 1 % Tongan , 0 . 1 % Samoan , 0 . 1 % Fijian , > 0 . 1 % Guamanian , > 0 . 1 % Native Hawaiian ) , 10 . 8 % from other races , and 5 . 4 % from two or more races . The population was 23 . 5 % Hispanic or Latino of any race ( 17 . 9 % Mexican , 1 . 3 % Salvadoran , 0 . 6 % Guatemalan , 0 . 6 % Puerto Rican , 0 . 5 % Nicaraguan , 0 . 3 % Peruvian , 0 . 2 % Cuban ) . The Chinese population of the Bay Area is concentrated in San Francisco , where 30 % of the Bay Area ' s Chinese American population resides , as well as in Oakland and in the Silicon Valley region of the South Bay , which is also home to a significant Indian American community . The San Francisco Bay Area is home to over 382 , 950 Filipino American s , one of the largest communities of Filipino people outside of the Philippines with the largest proportion of Filipino Americans concentrating themselves within Daly City . There are more than one hundred thousand people of Vietnamese ancestry residing within San Jose city limits , the largest population of any city in the world outside of Vietnam . There is a sizable community of Korean American s in Santa Clara County , and there is a large strip of Korean restaurants and businesses located in Santa Clara . East Bay cities such as Richmond and Oakland , and the North Bay city of Santa Rosa , have plentiful populations of Laotian and Cambodian s in certain neighborhoods . Pacific Islanders such as Samoan s and Tongan s have the largest presence in East Palo Alto , San Mateo , San Bruno , Redwood City and the Bayview - Hunters Point and Visitacion Valley neighborhoods of San Francisco . The Latino population is widely spread out through the Bay Area , but have largest populations in San Jose , in The Peninsula the cities of Redwood City , East Palo Alto , South San Francisco , as well the cities of San Mateo , and Daly City . East Bay cities namely Oakland , Richmond , Concord and Antioch , and in Sonoma County . San Francisco ' s Mission District is home to a thriving Mexican American community , as well as many residents of Salvadoran and Guatemalan descent . The African American population of the San Francisco Bay Area has always been significant in Oakland and Richmond , but other East Bay cities such as Antioch have received an influx of black residents . While mainly concentrated in the East Bay and in San Francisco , there are well established black neighborhoods located in the North Bay and in the South Bay . The South Park neighborhood of Santa Rosa was home to once a primarily black community until the 1980s , when many Latino immigrants settled in the area . The Marin City community in Marin County has a significant black population . In the South Bay , East Palo Alto has the highest population of African Americans . San Francisco ' s North Beach district is considered the Little Italy of the city , and was once home to a significant Italian American community . San Francisco and Marin County both have substantial Jewish communities . In 2007 the population density was 1 , 057 people per square mile . There were 2 , 499 , 702 housing units with an average family size of 3 . 3 . Of the 2 , 499 , 702 households , approximately one - third were renter occupied housing units , while two - thirds were owner occupied housing units . 12 . 7 % had a female householder with no husband present , 11 . 6 % of households had someone 65 years of age or older , and 27 . 4 % of households were non - families . The San Francisco Bay Area is one of the wealthiest regions in the United States , due , primarily , to the economic power engines of San Francisco , Oakland and San Jose . Pleasanton has the second highest household income in the country after New Canaan , CT . However , discretionary income is very comparable with the rest of the country , primarily because the higher cost of living offsets the increased income . Forty - seven Bay Area residents made the Forbes magazine ' s 400 richest Americans list , published in 2007 . Thirteen lived in San Francisco proper , placing it seventh among cities in the world . Among the forty - seven were several well - known names such as Steve Jobs , George Lucas , and Charles Schwab . The wealthiest resident was Larry Ellison of Oracle , worth $ 25 billion . A study by Capgemini indicates that in 2009 , 4 . 5 % of all households within the San Francisco - Oakland and San Jose metropolitan areas held $ 1 million in investable assets , placing the region No . 1 in the United States ( Metro New York City placed second at 4 . 3 % ) . As of 2007 , there were approximately 80 public companies with annual revenues of over $ 1 billion a year , and 5 – 10 more private companies . Nearly 2 / 3 of these are in the Silicon Valley section of the Bay Area . According to the May 2010 Fortune Magazine analysis of the US " Fortune 500 " companies , the combined San Jose - San Francisco - Oakland metropolitan region ranks second ( after metro New York City and before Chicago ) with 30 companies ( May 2011 , Fortune Magazine ) . Politics . The San Francisco Bay Area is widely regarded as one of the most liberal areas in the country . According to the Cook Partisan Voting Index ( CPVI ) , congressional districts the Bay Area tends to favor Democratic candidates by roughly 40 to 50 percentage points , considerably above the mean for California and the nation overall . All congressional districts in the region voted for Democrat Barack Obama over Republican John McCain in the 2008 Presidential Election . Over the last four and a half decades the 9 - county Bay Area voted for Republican candidates only twice , once in 1972 for Richard Nixon and again in for Ronald Reagan , both Californians . The last county to vote for a Republican Presidential candidate was Napa county in 1988 for George H . W . Bush . Districts were renumbered and boundaries changed after the 2010 census in accordance with new , less partisan , redistricting and primary election rules and procedures ( see Politics of California ) , but with little effect within the Bay Area . During the Base Realignment and Closure s ( BRACs ) of the 1990s , almost all the military installations in the region were closed . The only remaining major active duty military installations are Travis Air Force Base and Coast Guard Island . Climate . Because the hills , mountains , and large bodies of water produce such vast geographic diversity within this region , the San Francisco Bay Area offers a significant variety of microclimate s . The areas near the Pacific Ocean are generally characterized by relatively small temperature variations during the year , with cool foggy summers and mild rainy winters . Inland areas , especially those separated from the ocean by hills or mountains , have hotter summers and colder overnight temperatures during the winter . San Jose at the south end of the Bay averages fewer than of rain annually , while Napa at the north end of the Bay averages over 30 and parts of the Santa Cruz Mountains just a few miles west of San Jose get over 55 . In the summer , inland regions can be over 40 degrees Fahrenheit ( 22 degrees Celsius ) warmer than the coast . This large temperature contrast induces a strong pressure gradient , which results in brisk coastal winds which help keep the coastal climate cool and typically foggy during the summer . Additionally , strong winds are produced through gaps in the coastal ranges such as the Golden Gate , the Carquinez Strait , and the Altamont Pass , the latter the site of extensive wind farm s . During the fall and winter seasons , when not stormy , a high pressure area is usually present inland , leading to an offshore flow . While negatively impacting air quality , this also clears fog away from the Pacific shore , and so the best weather in San Francisco can usually be found from mid September through mid October . Winter storms are typically wet and mild in temperature during this time of year , being caused by cold fronts sweeping the eastern Pacific and often originating in the Gulf of Alaska . During November into mid March , winter storms are usually several days in length , wet and cool , with severely damaging storms rare . There is also recorded snowfall on San Francisco Bay Area peaks , such as Mount St . Helena , Tamalpais , Diablo and Hamilton . Snow levels range every given year from 1000 feet in Sonoma County to 2 , 000 ft in Contra Costa , San Mateo , and Santa Clara counties the during the winter . Greater recorded snowfall amounts are generally recorded once every 5 to 10 years . In February 2001 , 30 inches ( 76 cm ) of snow fell on Mount Hamilton ( 4360 ft ) , 17 inches on Mount Tamalpais ( 2 , 574 ft ) and 10 inches on Mount Diablo ( 3 , 864 ft ) . Occasionally during the late Summer or early Autumn , spells of warm humid weather will drift over the Bay Area from the Southwest Monsoon or from the residue of Western Pacific hurricanes near Mexico , usually bringing high variable clouds as well , and more rarely , high - based thunderstorm s . Ecology . Despite its urban and industrial character , San Francisco Bay and the Sacramento - San Joaquin Delta remain perhaps California ' s most important ecological habitats . California ' s Dungeness crab , Pacific halibut , and Pacific salmon fisheries rely on the bay as a nursery . The few remaining salt marsh es now represent most of California ' s remaining salt marsh , supporting a number of endangered species and providing key ecosystem services such as filtering pollutants and sediment s from the rivers . Most famously , the bay is a key link in the Pacific Flyway . Millions of waterfowl annually use the bay shallows as a refuge . Two endangered species of birds are found here : the California least tern and the California clapper rail . Exposed bay mud s provide important feeding areas for shorebird s , but underlying layers of bay mud pose geological hazards for structures near many parts of the bay perimeter . San Francisco Bay provided the nation ' s first wildlife refuge , Oakland ' s artificial Lake Merritt ( constructed in the 1860s ) and America ' s first urban National Wildlife Refuge , the Don Edwards San Francisco Bay National Wildlife Refuge ( SFBNWR ) ( 1972 ) . The Bay is also invaded by non - native species . Steelhead trout ( " Oncorhynchus mykiss " ) populations in California have dramatically declined due to human and natural causes . The Central California Coast distinct population segment ( DPS ) was listed as threatened under the Federal Endangered Species Act on August 18 , 1997 ; threatened status was reaffirmed on January 5 , 2006 . This DPS includes all naturally spawned anadromous steelhead populations below natural and manmade impassable barriers in California streams from the Russian River to Aptos Creek , and the drainages of San Francisco , San Pablo , and Suisun Bays . The U . S . National Marine Fisheries Service has a detailed description of threats . The Central California Coast Coho salmon ( " Oncorhynchus kisutch " ) Evolutionary Significant Unit ( ESU ) population is the most endangered of the many troubled salmon populations on the West Coast . It was listed as threatened on October 31 , 1996 and later downgraded to endangered status on June 28 , 2005 . The ESU includes all naturally spawned populations of coho salmon from Punta Gorda in northern California south to and including the San Lorenzo River in central California , as well as populations in tributaries to San Francisco Bay . The National Park Service has made major recent investments in restoring the tidal wetlands at the mouths of Lagunitas Creek and Redwood Creek including levee removal and placement of large woody debris in the creeks , which provide shelter to salmonids during heavy stream flows and flooding . Lagunitas Creek ' s coho population is especially important , as 80 % of the ESU depends on this stream draining the north slope of Mount Tamalpais . This year ' s coho count dropped to 64 from an average of 600 in previous years . Western Burrowing Owls ( " Athene cunicularia " ) were listed as a Species of Special Concern ( a pre - listing category under the Endangered Species Act ) by the California Department of Fish and Game in 1979 . California ' s population declined 60 % from the 1980s to the early ' 90s , and continues to decline at roughly 8 % per year . In 1994 , the U . S . Fish and Wildlife Service nominated the Western Burrowing Owl as a Federal Category 2 candidate for listing as endangered or threatened , but loss of habitat continues due to development of the flat , grassy lands used by the owl . A 1992 – 93 survey reported no breeding burrowing owls in Napa , Marin , and San Francisco counties , and only a few in San Mateo and Sonoma . The Santa Clara County population is declining and restricted to a few breeding locations , leaving only Alameda , Contra Costa , and Solano counties as the remnant breeding range . Despite organized protests at Kiper Homes ' Blue Ridge property in Antioch , California by " Friends of East Bay Owls " , one - way doors were installed in the birds ' burrows so that the owl families could not return to their nests in early 2010 . In addition , in 2008 , Mountain View , California evicted a pair of burrowing owls so that it could sell a parcel of land to Google to build a hotel at Shoreline Boulevard and Charleston Road . Eviction of the owls is controversial because the birds regularly reuse burrows for years , and there is no requirement that suitable new habitat be found for the owls . Much of the SFBNWR consists of salt evaporation ponds acquired from the Leslie Salt Company and its successor , Cargill Corporation through a series of land sales and donations . Many of these salt ponds remain in operation and produce salt used throughout the Western United States in food , agriculture , industry and medicine . The refuge pond support dense populations of brine shrimp , and therefore serving as feeding areas for waterfowl . In 2003 , the US Fish & Wildlife Service and California Department of Fish & Game entered one of the largest private land purchases in American history , with the state and federal governments paying $ 100 million for 15 , 100 acres ( 65 km² ) of salt ponds ( which government appraisers valued at $ 243 million prior to the acquisition ) in the south bay and 1 , 400 acres near the Napa River . SFBNWR and state biologists hope to restore some of the recently purchased ponds as tidal wetlands . Aquatic mammals recently re - colonizing the Bay Area include the California Golden Beaver ( " Castor canadensis " ) which is now established on Alhambra Creek in Martinez , Napa River and Sonoma Creek ; and North American River Otter ( " Lontra canadensis " ) which was first reported in Redwood Creek at Muir Beach in 1996 , and recently in Corte Madera Creek , and in the south Bay on Coyote Creek , as well as in 2010 in San Francisco Bay itself at the Richmond Marina . Sea otter ( " Enhydra lutris " ) were hunted to extinction in San Francisco Bay by about 1817 . Historical records reveal that the Russian - American Company snuck Aleuts into San Francisco Bay multiple times , despite the Spanish capturing or shooting them while hunting sea otters in the estuaries of San Jose , San Mateo , San Bruno and around Angel Island . The founder of Fort Ross , Ivan Kuskov , finding otter scarce on his second voyage to Bodega Bay in 1812 , sent Russian ships and hired an American ship to hunt otter in the Bay , catching 1 , 160 sea otter in three months . Humphrey the Whale , a humpback whale ( " Megaptera novaeangliae " ) , entered San Francisco Bay twice on errant migrations , and was successfully rescued and redirected each time in the late 1980s and early 1990s . This occurred again with Dawn and Delta a mother and calf in 2007 . The seasonal range of water temperature in the Bay is from about 8 °C ( 46 °F ) to about 23 °C ( 73 °F ) . Industrial , mining , and other uses of mercury have resulted in a widespread distribution of that poisonous metal in the bay , with uptake in the bay ' s phytoplankton and contamination of its sportfish . In November 2007 , a ship named " Cosco Busan " collided with the San Francisco – Oakland Bay Bridge and spilled over 58 , 000 gallons of bunker fuel , creating the largest oil spill in the region since 1996 . In March , 2012 a Bald eagle ( " Haliaeetus leucocephalus " ) nest was reported on the northwest arm of Lower Crystal Springs Reservoir and upper San Mateo Creek . This is the first bald eagle breeding pair on the San Francisco Peninsula since 1915 , when they nested in La Honda , almost one hundred years ago . The birds were once common in the Bay Area . While visiting Santa Clara County in 1855 , physician naturalist James G . Cooper described " a nest of this bird large enough to fill a wagon , built in a large sycamore tree , standing alone in the prairie . Habitat destruction and thinning of eggs from ( now banned ) DDT poisoning reduced the California state population to 35 nesting pairs at their lowest point . In the 1980s re - introductions began with the Santa Cruz Predatory Bird Research Group and the San Francisco Zoo began importing birds and eggs from Vancouver Island and northeastern California in the late 1980s . Geology and landforms . Multiple terrains . The area is well known worldwide for the complexity of its landforms , the region being composed of at least six terrane s ( continent al , seabed , or island arc fragments with distinct characteristics ) pushed together over many millions of years by the forces of plate tectonics . Nine out of eleven distinct " assemblages " have been identified in a single county ( Alameda ) . Diverse assemblages adjoin in complex arrangements due to offsets along the many faults ( both active and stable ) in the area . As a consequence , many types of rock and soil are found in the region . Formations include the sedimentary rocks of sandstone , limestone , and shale in uplifted seabeds , metamorphic serpentine rock , coal deposits , and igneous forms such as basalt flows , rhyolite outcroppings , granite associated with the Salinian Block west of the San Andreas Fault , and ash deposits of extinct yet relatively recently active ( 10 million years ) volcano s . Pleistocene - era fossil s of mammals are abundantly present in some locations . Vertical relief . The region has considerable vertical relief in its landscapes that are not in the alluvial plain s leading to the bay or in inland valleys . In combination with the extensive water regions this has forced the fragmented development of urban and suburban regions and has led to extensive building on poor soils in the limited flatland areas and considerable expense in connecting the various subregion s with roads , tunnels , and bridges . Several mountains are associated with some of the many ridge and hill structures created by compressive forces between the Pacific Plate and the North American plate . These provide spectacular views ( in appropriate weather ) of large portions of the Bay Area and include Marin County ' s Mount Tamalpais at 2 , 571 feet ( 784 m ) . Contra Costa County ' s Mount Diablo at 3 , 849 feet ( 1 , 173 m ) , Alameda County ' s Mission Peak at 2 , 517 to 2 , 604 feet ( 767 to 776 m ) , and Santa Clara County ' s Mount Hamilton at 4 , 213 ft ( 1 , 284 m ) , the latter with significant astronomical studies performed at its crowning Lick Observatory . Though Tamalpais and Mission Peak are quite lower than the others , Tamalpais has no other peaks and few hills nearby . Mission Peak is coast facing and is an interior mountain and therefore has excellent views of both sides . The three major ridge structures ( part of the Pacific Coast Range ) which are all roughly parallel to the major faultlines : Earthquake faults . The region is also traversed by six major slip - strike fault systems with hundreds of related faults , many of which are " sister faults " of the infamous San Andreas Fault , all of which are stressed by the relative motion between the Pacific Plate and the North American Plate or by compressive stresses between these plates . The fault systems include the Hayward Fault Zone , Calaveras Fault , Clayton - Marsh Creek - Greenville Fault , and the San Gregorio Fault . Significant blind thrust fault s ( faults with near vertical motion and no surface ruptures ) are associated with portions of the Santa Cruz Mountains and the northern reaches of the Diablo Range and Mount Diablo . Natural hazards . Earthquakes . The region is particularly exposed to hazards associated with large earthquakes , owing to a combination of factors : Some of these hazards are being addressed by seismic retrofit ting , education in household seismic safety , and even complete replacement of major structures such as the eastern span of the San Francisco – Oakland Bay Bridge . For an article concerning a typical fault in the region and its associated hazards see Hayward Fault Zone . For projected ground movement after selecting a locality and a generating fault see this ABAG web page Flooding . Some flooding occurs on local drainages under sustained wet conditions when the ground becomes saturated , more frequently in the North Bay area , which tends to receive substantially more rainfall than the South Bay . In one case , the Napa River drainage , floodplain developments are being purchased and removed and natural wetlands restored in the innovative Napa River Flood Project as the previous channelization of insufficient capacity around such developments was causing flooding problems upstream . Many of the local creeks have been channelized , although modern practice , and some restoration work includes returning the creeks to a natural state with dry stormwater bypasses constructed to handle flooding . While quite expensive , the restoration of a natural environment is of high priority in the intensively urbanized areas of the region . Windstorms and wildfires . Typically between late November and early March , a very strong Pacific storm can bring both substantial rainfall ( saturating and weakening soil ) and strong wind gusts that can cause trees to fall on power lines . Owing to the wide area involved ( sometimes hundreds of miles of coast ) , electrical service can be interrupted for up to several days in some more remote localities , but service is usually restored quickly in urban areas . These storms occasionally bring lightning & thunder . More rarely they even spawn tornadoes . For example , during the abnormal hurricane - like storm in early 2010 , a funnel cloud sparked an extremely rare Tornado Warning in Morgan Hill . In the spring and fall , strong offshore winds periodically develop . These winds are an especially dangerous fire hazard in the fall when vegetation is at its driest , as exemplified historically by the 1923 Berkeley Fire and the 1991 Oakland Firestorm . Mudslides and landslides . Some geologically unstable areas have been extensively urbanized , and can become mobile due to changes in drainage patterns and grading created for development . These are usually confined to small areas , but there have been larger problems in the Santa Cruz Mountains . Transportation . The Bay Area is served by many public transportation systems , including three international airports ( SFO , OAK , SJC ) , six major overlapping bus transit agencies ( AC Transit , Muni , SamTrans , VTA , Golden Gate Transit , County Connection ) , in addition to dozens of smaller ones . There are four rapid transit and regional rail systems including BART and Caltrain and two light rail systems ( San Francisco Muni Metro and VTA Light - rail ) . There are also several regional rail lines provided by Amtrak , notable the Capitol Corridor . In addition to rail lines , there are multiple public and private ferry services ( notably Golden Gate Ferry and Blue and Gold Fleet ) , which are being expanded by the San Francisco Bay Water Transit Authority . The regional ferry hub is San Francisco Ferry Building . AC Transit and some other agencies provide an extensive network of express " transbay " commuter buses from the suburbs to San Francisco Transbay Terminal . The freeway and highway system is very extensive ; however , many freeways are heavily congested during rush hour , especially two of the trans - bay bridges ( Golden Gate and Bay Bridge ) . Furthermore there are some large gaps in the highways which run onto city streets in San Francisco , partially due to the Freeway Revolt ( SF Board of Supervisors decisions made in 1959 , 1964 and 1966 ) , which prevented completion of freeways connecting the San Francisco – Oakland Bay Bridge western terminus ( Interstate 80 ) with the southern terminus of the Golden Gate Bridge , and U . S . 101 through San Francisco , and additionally due to the destruction of several of those very freeway structures that sparked the revolt , which were damaged in the 1989 Loma Prieta earthquake and subsequently removed rather than being reinforced or rebuilt . Higher education . The region is home to many colleges and seminaries , most notably the University of California , Berkeley , the University of California , San Francisco and Stanford University . In addition , the Bay Area is home to two of the twenty - eight Jesuit universities in the U . S . : Santa Clara University ( founded in 1851 ) , and University of San Francisco ( 1855 ) ; these are also the two oldest California colleges . San Jose State University is the founding campus of the California State University ( CSU ) system , and is the oldest public institution of higher education on the West Coast of the United States . Saint Mary ' s College of California was founded in 1863 by the Roman Catholic Archdiocese of San Francisco . In 2008 , there were approximately 588 , 000 students enrolled in college or graduate school . The San Francisco Bay Area population is near the top in the Nation for overall education level with approximately 41 percent of residents aged 25 years and over having a bachelors degree or higher . The San Francisco and San Jose Primary Metropolitan Statistical Areas rank third and fourth in college graduates , ahead of Boston and behind only Boulder – Longmont , CO PMSA and Stamford – Norwalk , CT PMSA . The Oakland PMSA ranks eleventh . Culture . The Bay Area is host to numerous cultural events , including annual festivals and fairs . Many prominent writers make their homes there , and have developed a local literary culture , with a supportive network of booksellers , focused on the Northern California Independent Booksellers Association . Music . Classic rock . San Francisco proper was headquarters for the hippie counterculture of the 1960s and the music scene that became associated with it . One of the area ' s most notable acts was The Grateful Dead , formed in 1965 , who played regularly at the legendary venue " The Fillmore Auditorium " . Other local artists in that movement included Jefferson Airplane and Janis Joplin ; all three would be closely associated with the 1967 Summer of Love . Jimi Hendrix , although born in Seattle and later a resident of London , England , had strong connections to the movement and the metropolitan Bay area , as he lived in Berkeley for a brief time as a child and played many local venues in that decade . Creedence Clearwater Revival ( of El Cerrito ) would gain traction as an associated band of the . Rock and Roll Hall of Fame legend Neil Young has lived in the Bay Area in La Honda , CA for more than 40 years . Carlos Santana from San Francisco became famous in the late 1960s and early 1970s with his Santana band which pioneered a blend of rock , salsa , and jazz fusion . Journey formed in 1973 in San Francisco , by former members of Santana . The Doobie Brothers , from San Jose , had a successful career with several albums earning RIAA gold certification . The early 1970s sounds of the Tower of Power from Oakland , Sly and the Family Stone and Pablo Cruise all came from the Bay Area . Heavy metal . During the 1980s and early 1990s , the Bay Area was home to one of the largest and most influential thrash metal scenes in the world , containing acts like Metallica ( although Metallica had initially formed in Los Angeles , it wasn ' t until their relocation to El Cerrito in 1983 that Cliff Burton and Kirk Hammett joined as bassist and lead guitarist ) , Exodus , Laaz Rockit , Death Angel , Vio - lence , Forbidden , Testament . Many death metal bands had also formed in the area , including Autopsy , Possessed ( considered one of the first in the genre ) , and in the ' 90s , Impaled , Exhumed and Vile . Also , an avant - garde metal scene has emerged in the Bay Area with bands such as Giant Squid , Grayceon , and Ludicra . Sludge band Neurosis and groove metal / post - thrash bands Machine Head and Skinlab formed in Oakland . In the alternative metal and nu - metal scenes worldwide , Faith No More ( from San Francisco ) and Primus ( from El Sobrante , and featuring former Possessed guitarist Larry LaLonde ) have been considered progenitors to both subgenres . Heavy metal / hard rock icon Joe Satriani , also hails from the Bay Area ( Berkeley ) . Rising Deathcore band , Rings of Saturn , is also from Bay Area . Alternative rock . Many bands of the 1990s post - grunge era started and still reside in the Bay Area , including Third Eye Blind ( of San Francisco ) , Counting Crows ( of Berkeley ) and Smash Mouth ( of San Jose ) , all of whom have received extensive radio play across the world and released multi - platinum records during their career . Punk . The Bay Area saw a large punk movement from the 70s to the present . Bands such as the Dead Kennedys , The Avengers , Flipper , D . R . I . , M . D . C . and Operation Ivy were popular in the ' 70s and ' 80s , with later bands such as Rancid , Green Day and AFI all coming out of Berkeley . The Dwarves are residents of San Francisco , and are considered to be pioneers of the punk and hardcore movement . Rap and hip hop . The Bay Area is the home of the hyphy movement , which started in the early to mid - ' 90s . The genre which was pioneered by rappers Andre " Mac Dre " Hicks , Too Short , Keak Da Sneak , Mistah Fab , E - 40 , Lil B and Yukmouth , is now becoming more popular throughout the world . Hyphy themes such as ghost riding , thizzin ' and going dumb are now common in other parts of the country . The Bay Area was also home to rap legend Tupac Shakur who lived in Marin City , about north of San Francisco . The rap group Digital Underground originally hailed from Oakland . MC Hammer , and the Hieroglyphics hip hop crew , which is composed of local artists including the Souls of Mischief and Del tha Funkee Homosapien . Cindy Herron of En ' Vogue attended Balboa High School in the late 1970s . Usher is commonly known to visit at times as well . Media . The Bay Area is one of the largest media market s in the United States . According to Nielsen Media Research , the Bay Area ranks ( as of the 2005 – 2006 television season ) as the nation ' s sixth - largest " Designated Market Area ( DMA ) " , with 2 , 355 , 740 " TV Homes " , representing 2 . 137 % of the United States Total .