page_title: Environment of California
section_title: Population and transportation
hierarchical_section_title: Environment of California / Population and transportation
caption_attribution_description: English: A field of dozens of oil wells just offshore, at Summerland (Santa Barbara County), before 1906. Original caption reads: "Oil wells at Summerland, Santa Barbara County, California, showing the ocean bluffs in front of Sumerland [sic], the wharves and derricks over the wells."
context_page_description: The environment of California describes results of human habitation of the State of California.
context_section_description: California's aboriginal population of about 300,000 was distributed in relatively self-sufficient groups with subsistence resources on the coastal wetlands near the mouth of the Smith River, along the Klamath River and its interior wetlands, on the coastal wetlands surrounding Humboldt Bay, on the wetlands surrounding San Francisco Bay and the rivers of the California Central Valley, along the Salinas River, and along the coastal wetlands between Morro Bay and San Diego Bay.  Early European trade was by ship, but El Camino Real extended northward along the southern California coast and through the California Coast Ranges from Mexico to San Francisco Bay to link individual missions with seaports.  San Francisco Bay became the most important seaport for the gold rush and ferries of San Francisco Bay carried trade between the seaport and mining areas.  The California Trail became the first important land link between San Francisco Bay and the eastern United States during the gold rush and became the route of the First Transcontinental Railroad in 1869.  The gold rush brought approximately 200,000 new residents to California, and 36% of Californians lived around San Francisco Bay by 1870.  Lumber from coastal redwood forests was transported to San Francisco by ships.  Redwood proved poorly suited for railroad ties, so fast-growing Australian eucalypts were widely planted to provide future supplies.
  San Francisco Bay remained the focus of a railway network extending north and south until Atchison, Topeka and Santa Fe Railway completed a transcontinental rail link to Los Angeles and San Diego in 1885.  Eastbound rail shipment of citrus began in 1890.  Petroleum was discovered in 1892, and the first offshore drilling occurred at Summerland Oil Field in 1896.  Hollywood's film industry and shift of the United States Navy Battle Fleet home port to San Pedro in 1919 accelerated growth of southern coastal cities to 36% of the state population by 1920.
  As California petroleum production peaked, the United States Highway System of 1925 included routes paralleling older transportation corridors.  U.S. Route 101 followed El Camino Real and extended through the redwoods to Humboldt Bay.  U.S. Route 99 extended northward from Los Angeles following railways through the Central Valley; and the Lincoln Highway and U.S. Route 66 followed the transcontinental rail routes from San Francisco Bay and Los Angeles, respectively.  Popularity of automobile travel encouraged construction of California Route 1 connecting California State Beaches, U.S. Route 395 through the Sierra Nevada, and the Arroyo Seco Parkway as the first freeway.  Smog was recognized as an air pollution problem in 1954 as Los Angeles Railway, Pacific Electric Railway and Key System public transport facilities were dismantled during the great American streetcar scandal.  Southern California cities were home to 51% of Californians when the Interstate Highway System arrived in 1959, while 26% lived around San Francisco Bay.  Lincoln Highway became Interstate 80, Route 66 became Interstate 40, and Interstate 5 extended from San Diego through Los Angeles and north up the rain shadowed western side of the Central Valley and the eastern end of San Francisco Bay.
  Modern commuter rail service includes Bay Area Rapid Transit, Caltrain, Muni Metro, Metro Rail (Los Angeles County), San Diego Trolley, Sacramento Regional Transit District, Santa Clara Valley Transportation Authority light rail, and Amtrak's Pacific Surfliner and Capitol Corridor.  In 2010, 9 million Californians (24% of the population) lived around San Francisco Bay and 21 million (57% of the population) lived in the southern coastal cities.
caption: 20th century petroleum extraction helped the city of Los Angeles become one of the largest in the United States.
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