For 40 years, photographer and historian John Margolies drove across America photographing roadside architecture. He documented coffee shops shaped like coffeepots, hot dog–shaped fast-food stands, even a Shell gas station that looked like, you guessed it, a giant scallop shell. Margolies had appreciated these unpretentious buildings since he was a kid, and he captured them unsentimentally. 

These joyfully literal buildings have a name: architectural ducks. The term—coined by Denise Scott Brown, Robert Venturi and Steven Izenour in their seminal book, Learning from Las Vegas—describes structures that incorporate their function into their very fabric. The concrete Big Duck shop, built by a Long Island duck farmer, inspired the moniker. Scott Brown, Venturi and Izenour differentiat...