The 1920s and 1930s saw the birth of modernism in the United States, a new aesthetic, based on the principles of the Bauhaus in Germany: its merging of architecture with fine and applied arts; and rational, functional design devoid of ornament and without reference to historical styles. Alfred H. Barr Jr., the then 27-year-old founding director of the Museum of Modern Art, and 23-year-old Philip Johnson, director of its architecture department, were the visionary young proponents of the modern approach. Shortly after meeting at Wellesley College, where Barr taught art history, and as Johnson...