The Washington Monument is the tallest building in Washington D.C. at 555 feet (169 meters), and also the tallest masonry tower in the world (masonry is the building of structures from individual units laid in and bound together by mortar). This marble building has a very fascinating history. The idea for the monument was first proposed in 1783 by Congress, but some fifty years later it became apparent that if left to congressional action, a monument would not be built. Headed by a man named George Watterson, the Washington National Monument Society was organized in 1883 to collect money for the monument. A man named Robert Mills had the winning design for the monument depicted here. After 12 years, the society had only raised $87,000 of the $1 million needed to build the monument. In order to reduce costs, the society decided to build only the obelisk. So the construction began in 1848.