The Farallon Islands lie almost 30 miles outside the entrance to San Francisco Bay and are comprised of over 20 islands, islets, sea stacks, and rocks, which span a seven-mile stretch of the Pacific Ocean. Nineteenth-century sailors called them "the Devil's Teeth," in reference to their extreme hazard to navigation, and hundreds of shipwrecks, disasters, drownings, and deaths have occurred here. The sixth lighthouse on the West Coast was lit on Southeast Farallon Island in 1855. Only Southeast Farallon supports historic structures, several of which are maintained for management purposes. Southeast Farallon once served as home to keepers from the Bureau of Lighthouses (1853-1939), the US Coast Guard (1939-1972), and at various times the US Navy. Today, the islands are home to millions of seabirds and five species of pinnipeds. Because of their biological importance, the islands are not open to the public. They are managed by the US Fish and Wildlife Service in collaboration with Point Blue Conservation Science. Visitors can explore the islands by boat, at speeds of five miles per hour and from a distance the length of a football field for excellent viewing of globally significant wildlife populations.