Adolph Sutro made his fortune boring the Sutro Tunnel through the Comstock Lode in Nevada, then bought up one-twelfth of San Francisco's total acreage. The baths were his gift to the city's working class -- a place where anyone could swim in heated saltwater pools for the price of a streetcar ride. The structure was a marvel of Victorian engineering: 100,000 square feet of glass roofing, 600 tons of iron framework, and 3.5 million board feet of lumber. A turbine pump built inside a sea-level cave could fill the pools at 6,000 gallons per minute. The Ferries and Cliff House Railroad delivered visitors along the cliffs of Lands End, and Thomas Edison's film crew captured the spectacle on camera in 1897, making the baths some of the earliest moving images shot in San Francisco.

In 1897, just a year after the baths opened, a man named John Harris was denied entry because of his race. Harris sued Adolph Sutro and won, establishing an early legal precedent against racial segregation in public facilities. The case set a marker for the future of civil rights law in California, decades before the national conversation caught up. That this battle was fought at a swimming pool is no accident: public bathing facilities were among the most fiercely segregated spaces in American life, and remained so in many states well into the 1960s. Harris's victory made the Sutro Baths one of the few integrated public swimming establishments in the country at the turn of the century.

The baths were spectacular but economically punishing. Operating and maintenance costs devoured revenue. By the 1950s, the Sutro estate had sold the property to George Whitney, who shut down half the building and converted the southern portion into an ice skating rink. A tram connecting the Cliff House observation deck to Point Lobos operated from 1955 to 1966, but could not save the business. In 1964, the property was sold to developers planning a high-rise apartment complex. Then, in 1966, while the building was already being demolished, a fire destroyed what remained. Investigators determined the cause was arson. The developers left San Francisco and collected insurance money. The sequence of events has fueled speculation ever since.

What remains is strangely beautiful. Concrete walls trace the outlines of the pools. Blocked-off stairways lead to tunnels with deep crevices. The Pacific surges through gaps in the foundation, filling the ruins with the sound and spray of the ocean. The site is now part of the Golden Gate National Recreation Area, drawing hikers and photographers who find the skeletal remains more compelling than the building itself ever was. Harold and Maude filmed a scene among the ruins in 1971. Cory Doctorow set key passages of his novels Little Brother and Homeland here. The ruins have become one of San Francisco's most atmospheric landmarks precisely because they are ruins -- a monument to ambition, decline, and the ocean's patient reclamation of everything built along its edge.