In 1835, the Mexican government ceded Rancho Sausalito, about 20,000 acres in southern Marin, to William Richardson. By 1900, considerable development had occurred: in the north, two towns, Sausalito and Mill Valley; in the south, Fort Baker, Fort Barry and Fort Cronkhite; in between, several dairy ranches. Of major significance was the Point Bonita Lighthouse on the southwest corner. It had been in operation since 1856 along with other lighthouses serving San Francisco Bay ship traffic at Fort Point, Alcatraz and South Farallon. The illumination of lighthouses had evolved over time. Initially there were candles then lamps burning whale oil, lard oil, vegetable oil and, by the 1870s, kerosene. By 1900, electricity had replaced kerosene lamps, but coal fired boilers still generated steam for the sirens, whistles and foghorns. The original Point Bonita Lighthouse, a 56-foot brick tower, was too high. The West Coast has dense high fog, which leaves lower elevations clear. In 1877, the lighthouse was moved to its current lower location. Point Bonita was the last manned lighthouse on the California coast. It was added to the National Register of Historic Places in 1991. The United States Coast Guard currently maintains the light and fog signal.