Point Diablo extends about 600 feet (183m) south from the Marin Headlands, roughly midway between Point Bonita to the west and Lime Point to the east, about 6 miles (10km) northwest of San Francisco and 2.7 miles (4km) south-southwest of Sausalito, California. The point earned its name due to the navigational challenges it poses for ships entering or exiting the Golden Gate in foggy conditions. The Marin Headlands form the northern shore of the Golden Gate and are named after Chief Marin of the Licatiut band of Coast Miwok. He was also known by his Native name, Huicmuse, and his baptized name, Marino. These headlands are composed of rock formations collectively called the Franciscan Complex. This complex was created through the accretion of oceanic rock and sediments onto the North American continental plate during the tectonic process of subduction. The southern end of the Marin Headlands consists of rocks from a unique tectonostratigraphic terrane, part of the Franciscan Complex. It features pillow basalt overlain by radiolarian chert, which is in turn overlain by graywacke sandstone and shale. The basalt formed during the Early Jurassic, about 190 million years ago, at a mid-ocean ridge. It was subsequently buried by radiolaria during the terrane’s long, 100-million-year journey across the ocean. Eventually, the terrane reached a deep ocean trench, where Cretaceous turbidites, derived from an eroding volcanic arc, buried the chert. This volcanic arc was likely related to an ocean-continent subduction zone, as the turbidites, which lithified into graywacke sandstone, contain minerals such as feldspar from continental rocks. This may indicate the approach of the Marin oceanic terrane to the North American plate, followed by partial subduction and accretion, forming the present-day headlands. The radiolarian chert suggests that the basalt formed near the equator and was carried eastward or northeastward toward North America. The terrane entered a trench south of its current position, likely around southern Mexico, and was transported northward up to 2,500 miles (4,000 km) by right-lateral transform faulting. Point Diablo comprises erosion-resistant serpentinite at the outermost tip and chert at the base.

The Coast Miwok were hunter-gatherers whose ancestors occupied the Marin Peninsula for millennia. Around 600 historical village sites have been identified. Francis Drake provided the first documentation of the Coast Miwok during a five-week encounter in 1579 when he stopped to repair his ship, the Golden Hind. In 1595, Sebastião R. Soromenho sailed from Manila on the San Agustin, reaching the California coast between Point Saint George and Trinidad Head. He followed the coast south to Drakes Bay, where he was greeted by the Coast Miwok in a manner similar to Drake 16 years earlier. In 1776, Mission San Francisco de Asis, also known as Mission Dolores, was founded, and by 1817 it had evangelized about 850 Coast Miwok. That year, Mission San Rafael was established on the Marin Peninsula, but by then the only Miwok remaining on traditional lands were north of Point Reyes. In 1834, following Mexico’s independence from Spain, mission lands were secularized, freeing the Coast Miwok from Franciscan control. In 1835, Governor José Figueroa granted 19,752 acres (7,993 ha) of Rancho Saucelito to José Antonio Galindo. In 1838, Galindo was arrested for the murder of José Doroteo Peralta, and Rancho Saucelito was re-granted to William A. Richardson by Governor Juan Alvarado. Many of the remaining Coast Miwok began to live in servitude on the ranchos for land grant owners. By 1850, at the onset of California statehood, many Coast Mewok of the M’rinn Peninsula were working as farm laborers on ranchos that were rapidly passing from Mexican to Euro-American ownership. In the 1890s, the first military installations were built on the M’rinn Headlands to prevent hostile ships from entering San Francisco Bay. The gun batteries at Kirby Cove to the east of Point Diablo and at Black Sands Beach to the west, are examples of fortifications from the pre-World War I period. During World War II, Batteries Wallace, Townsley, and 129 on Hawk Hill were built into the mountain to protect against aerial bombardment. In the Cold War era, radar sites were established atop Hawk Hill and Hill 88. Shelters were constructed in hillsides to shield military personnel from nuclear, biological, or chemical attacks. In 1972, President Richard Nixon established the Golden Gate National Recreation Area ,and today, all military sites in the headlands are decommissioned and returned to civilian use.

Beginning in 1848, the California Gold Rush significantly increased vessel traffic along the coast and San Francisco Bay, highlighting the urgent need for navigational aids to prevent shipwrecks. In 1852, the US Congress established a nine-member Lighthouse Board to assume control of the lighthouse system from the US Treasury Department. The board divided the system into 12 districts, placing the Pacific Coast and Pacific Islands in District 12. It was tasked with constructing lighthouses on the West Coast and acquiring Fresnel lenses for all lighthouses. A survey team was dispatched to California to identify critical sites for navigational aids. Fort Point light and Alcatraz Island light were built in 1853. In 1854, a lighthouse was constructed at Point Bonita on the northern shore of the Golden Gate. A brick structure for the Lime Point Lighthouse was completed in 1883. Finally, in 1906, the Mile Rocks Lighthouse, located about 0.4 miles (0.64 km) from the southern shore, was completed. In 1923, the US Lighthouse Service built a navigational aid at Point Diablo, a steep, rocky headland about 1.2 miles (2 km) west of the Golden Gate Bridge. A small white shack with a pitched red roof was constructed 85 feet (26 m) above the water. Originally, it housed two lanterns and an electric siren, which the lightkeepers at Lime Point managed. A telephone and electric line were installed between Lime Point and Point Diablo, allowing lightkeepers to monitor the semi-automated station. Nevertheless, they had to visit Point Diablo weekly to clean the light and oil the fog signal. In 2007, the navigation light was mounted on a post beside a square, one-story wooden fog signal building. Today, solar panels power the modern beacon, which displays a white light three seconds on and three seconds off. The fog signal operates continuously, sounding every 15 seconds. The station is accessible only by boat and is closed to the public. Read more here and here. Explore more of Point Diablo and Marin Headlands here: