Chimney Rock is an islet off the eastern headland of the Point Reyes Peninsula, connected to it only at low tide, about 3 miles (4.8 km) east of the Point Reyes Light and 10 miles (16 km) southwest of Inverness, California. The headland lies within Point Reyes National Seashore and separates the western and southern shores of Drakes Bay from the Pacific Ocean. Point Reyes was formed nearly 29 million years ago, though the rocks visible today date from the Late Jurassic, about 159 million to 144 million years ago, when the oceanic Farallon Plate was subducting beneath the North American continental plate. The area now sits on the Pacific Plate, within a region called the Salinian Block—a zone between two sets of strike-slip faults, 25 to 44 miles (40–70 km) wide and over 310 miles (500 km) long, lying close to the San Andreas Fault. East of the fault, Point Reyes consists of the Franciscan Complex, composed of highly deformed and metamorphosed graywacke, mudstone, volcanic material, chert and limestone. To the west lies Late Cretaceous-age (about 100 million to 66 million years ago) granite overlain by more recent sedimentary rock. Chimney Rock itself consists of erosion-resistant porphyritic granodiorite, once surrounded by more readily erodible conglomerate from the early Eocene (about 56 million to 49 million years ago).

Before the railroad and highway networks, shipping was the primary means of transporting cargo and passengers. The Point Reyes Peninsula posed a significant hazard to coastal navigation because of its proximity to the port of San Francisco: the point extends 10 miles seaward from the mainland and is frequently shrouded in fog. After dozens of shipwrecks, a lifesaving station was built in 1888 on the sheltered western shore of Drakes Bay. It was replaced in 1927 and operated until 1968 as the Point Reyes Lifeboat Station. Built on a rare sandy stretch of an otherwise rocky coastline near Chimney Rock, the station was exposed to the very conditions that made it necessary: heavy fog, high winds and dangerous surf. The boathouse, the principal structure, stands at the base of the headland’s hills and cliffs, its piers and lifeboat-launching marine railway extending into the bay; the remainder of the complex is perched on the hillside above. During its mid-20th-century operation, observers walked the beaches in four-hour shifts, watching for vessels in distress. The station is now a historic property managed by the National Park Service as part of Point Reyes National Seashore.

During winter, northern elephant seals haul out on the narrow rocky beaches along the Drakes Bay side of Point Reyes. They take their name from their great size and from the male’s large proboscis, used to produce extraordinarily loud roaring calls, particularly during mating competition. Beginning in the 18th century, northern elephant seals were hunted extensively for the oil rendered from their blubber; by the end of the 19th century the population may have fallen to as few as 20–40 individuals. A single bull could yield nearly 25 gallons (114 liters) of oil. Mexico banned the hunting in 1922, followed shortly by the United States; since the early 20th century both countries have protected the species by law. American protections were further strengthened by the Marine Mammal Protection Act of 1972. The population has since recovered at an average rate of 6% a year, and the worldwide total is now estimated at 210,000. Read more here and here. Explore more of Chimney Rock and Point Reyes Peninsula here: