The Ferris Wheel at the World's Columbian Exposition, Chicago, IL, 1893

Image Donated by Corbis-BettmannBuilt for the 1893 World's Columbian Exposition, which commemorated the 400th anniversary of Columbus's trip to America, the Ferris Wheel was supported by two 140-foot steel towers connected by a 45-foot axle. To insure the safety of his "gargantuan Ezekiel's Wheel", William Ferris required the Bethlehem Steel Company to make the 45-foot, 70-ton axle six times more stout than was needed to be safe. Ferris's axle, the weight of a large locomotive, was at that time the heaviest piece of steel ever forged.