The ice cream cone. The zipper. The Ferris wheel. The X-ray machine. The inventions that debuted at world’s fairs are vast and varied. The National Building Museum pays homage to this spirit of innovation with the exhibition “Designing Tomorrow: America’s World’s Fairs of the 1930s.” In the midst of the Great Depression, the U.S. hosted a whopping six of these exhibitions, some in obvious locales (New York, Chicago), some in not-so-obvious (ahem, Cleveland?). The fairs spurred industry and cutting-edge design—the 70-year-old posters from the fairs would look right at home on the walls of any modernist devotee—and produced some truly remarkable architecture. Unfortunately, structures like the Elephant Towers in San Francisco, the General Motors Building in New York, and the U.S. Government Building in Chicago can only be enjoyed through photographs—the buildings were torn down shortly after their respective fairs concluded. The wastefulness is as breathtaking as the architecture.

THE EXHIBITION IS ON VIEW 10 A.M. TO 5 P.M. MONDAYS TO SATURDAYS AND 11 A.M. TO 5 P.M. SUNDAYS TO JULY 10, 2011 (CLOSED DEC. 25 AND JAN. 1) AT THE NATIONAL BUILDING MUSEUM, 401 F ST. NW. FREE. (202) 272-2448.