|Historical Notes||"The Space Needle, flame-topped symbol of the fair, soars to the height of 606 feet. It is supported by three curved steel legs, 500 feet high. It is topped by a circular, glass-enclosed housing that contains an observation deck and a revolving restaurant... The foundation of the Needle is a Y-shaped reinforced concrete block weighing more than 5, 850 tons. It is buried 30 feet in the ground. The Needles' legs are attached to it by 72 steel anchor bolts, four inches in diameter and 31 1/2 feet long. Although there are 3, 500 tons of steel in the superstructure, the base is so massive that the center of gravity for the whole unit is only slightly above ground level." (Century 21 Exposition. (1962). Official Guide Book, Seattle World's Fair 1962. Seattle: Acme Publications. p. 143)|
The Century 21 Exposition, also known as the Seattle World's Fair, took place between April 21 and October 21, 1962.