American bathrooms haven’t grown only in number. As the square footage per person in a new single-family home doubled from the 1970s to the 2010s, so too did the typical size of a bathroom—from 35 square feet to 70, according to Hoagland. They’ve also grown in importance, taking on new, ever more fanciful roles, serving as “power room, laundry room, phone booth, library, gymnasium, storage closet, and, for the affluent at least, a place of sybaritic luxury,” as Newsweek wrote in 1965.

Larger and more voluminous bathrooms, with their deeper shower shelves and taller medicine cabinets, gave individuals more room for beauty equipment, lotions, serums, shampoos, conditioners, soaps, creams, and makeup brands. Since Diane von Furstenberg published The Bath, her influential ode to the commode, in 1993, affluent Americans have transformed their bathrooms into technological marvels, with Jacuzzis, steam showers, rainfall heads, and other gizmos to reproduce various tropical microclimates.

This is the bathroom’s impressive 100-year evolution in the United States: What was once a foul cesspool has become a human car wash.