The Washington Monument Was the World's Tallest Building

The tallest building on Earth once stood in Washington, D.C. The U.S. National Park Service states that the Washington Monument was the tallest building in the world upon its completion in 1884, standing 555 feet, 5-1/8 inches. In reaching that height it surpassed the Cologne Cathedral. The number was not chosen at random. The original plan called for 600 feet, but the engineer in charge was persuaded to make the height ten times the width of the base, which made the optimal height 555 feet. Getting there took a long time. The monument was built in two phases, one private, from 1848 to 1854, and one public, from 1876 to 1884. Near the top, the builders angled buttresses inward to support the 300-ton marble pyramidion that caps the monument.