The Centennial Exposition, the first American World's Fair, took place in Philadelphia in 1876. The exposition included the construction of over 200 buildings, most temporary, including the Main Exhibition Building, designed by Joseph M. Wilson and Henry Petit, which was the largest building in the world at the time. The Exposition's two major permanent buildings were Horticultural Hall and Memorial Hall, both designed by Herman J. Schwarzmann. Horticultural Hall (demolished 1955) was a Moorish-style glass-and-iron structure built as a tribute to London's Crystal Palace. The Beaux-Arts-style Memorial Hall (now home to the Please Touch Museum) was constructed of brick, glass, iron and granite.