The Illinois

The Illinois
An Artist's sketch of the illinois
General information
Status	Vision
Type	Office
Location	Chicago, Illinois, U.S.
Height
Antenna spire	5,680 ft (1,730 m)
Roof	5,280 ft (1,610 m)
Technical details
Floor count	528
Floor area	18.46 million ft2(1.71 million m2)
Lifts/elevators	76

The Mile High Illinois, Illinois Sky-City, or simply The Illinois is a visionary skyscraper that is over 1 mile (1,600 m) high, conceived and described by noted American architect Frank Lloyd Wright in his 1957 book, A Testament. The design, intended to be built in Chicago, included 528 stories, with a gross area of 18,460,000 square feet (1,715,000 m²). Wright stated that there would have been parking for 15,000 cars and 100 helicopters.

If built, it would top the list of the tallest building in the world by far, being more than four times the height of the Empire State Building, and twice as tall as the world's current tallest building, the Burj Khalifa, the design of which is said to have been inspired by that of The Illinois.

Wright believed that it would have been technically possible to construct such a building even at the time it was proposed. At the time, the tallest skyscraper in the world was New York's Empire State Building, at less than a quarter the height suggested for the Illinois. It probably would have been possible to erect a self-supporting steel structure of the required height, but there are a number of problems which occur when a building is that tall.

The material used to build tall towers at the time, steel, is quite flexible. This allows towers to sway substantially in the wind, causing discomfort for occupants of the higher floors. Though Wright acknowledged this problem in his original proposal, he believed the tripod design of this tower (similar to that of the CN Tower, which was not designed until a decade after Wright's death) combined with its tensioned steel frame and the integral character of its structural components would counteract any oscillation. This also could have been solved by placing a tuned mass damper somewhere within the tower as was done in the Citigroup Center and Taipei 101, although this design innovation was not well known until decades later. The late 1990s and early 2000s saw substantial increases in the load-bearing strength of concrete, making it possible to build entirely in this stiff material.