San Francisco Bay

This famous bay was the epicenter of American settlement in the Far West during the 19th century. From the 1820s onward, American presidents and expansionists coveted the bay as a great natural harbor in the Pacific. After many failed efforts to buy the bay and varying areas around it, the US Navy and Army seized the region from Mexico during the Mexican-American War (1845-1848). During the California gold rush of 1848-1850s, San Francisco Bay instantly became one of the world's greatest seaports, dominating shipping and transportation in the American West until the last years of the nineteenth century. The bay's regional importance became paramount when in 1869 the transcontinental railroad located its western terminus in Oakland. San Francisco Bay continues to support some of the densest industrial production and urban settlement in the United States. The San Francisco Bay Area is the American West's second-largest urban area with approximately 8 million residents.

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 marshes 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 sediments from the rivers. Most famously, the bay is a key link in the Pacific flyway. Millions of waterfowl annually use the nation's first wildlife refuge, Oakland's artificial Lake Merritt (constructed in the 1860s) and America's first urban National Wildlife Refuge, the San Francisco Bay National Wildlife Refuge (1962). Tellingly, much of the SFBNWR consists of salt evaporation ponds purchased or leased from Leslie Salt Company and its successor, Cargill Corporation. These salt ponds produce salt for a variety of industrial purposes, including chlorine bleach and plastics manufacture, as well as supporting dense populations of brine shrimp, and therefore serving as feeding areas for waterfowl. In 2003, California and Cargill entered one of the largest private land purchases in American history, with the state and federal governments paying about $200 million for salt ponds around the bay. SFBNWR and state biologists hope to restore some of the recently purchased ponds as tidal wetlands.

San Francisco Bay is spanned by five bridges: the Golden Gate Bridge (which was the largest suspension bridge ever built at the time of its construction), the Richmond-San Rafael Bridge, the San Francisco-Oakland Bay Bridge, the Hayward-San Mateo Bridge and the Dumbarton Bridge.

The southern part of the San Francisco Peninsula including the city of San Jose is known as the Silicon Valley for its high concentration of high-tech, semiconductor and computer-related industry.

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