The trunk of a rubber tree from Liberia, Africa at the Firestone exhibition building in Chicago, Illinois. From 1933 to 1934, Chicago hosted the "Century of Progress International Exposition" to celebrate the city's centennial. The theme of the fair was technological innovation. The Firestone Tire and Rubber Company's contribution to the fair was an exhibition building that allowed people to see how rubber trees are turned into tires. Approximately 10,000,000 visitors walked through an assembly line that produced a tire every fifteen minutes.