In 1939 and 1940, a world that was beginning to climb out of the Great Depression and about to descend into World War II had a brief glimpse of a bright future at the New York World's Fair. After the Fair shut its gates for the last time in 1940, the organizers took their meticulous records of the event and presented them to the New York Public Library for safekeeping. 70+ years later, the library has opened the Fair to the world again in the form of NYPL Biblion: World's Fair, an innovative and exhaustively detailed history of the Fair in an interactive iPad app. In this review, I'll discuss this amazing app -- the first in a hopefully long series exploring the NYPL's collection -- and show you some screen shots of the app in action.