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Timeline. 1  1965: Plans for the John Hancock Center are announced. 2  1969: Construction is completed. 3  1972: The Hancock Center is surpassed by the Standard Oil Building (now the Aon Center) as the tallest building in Chicago.  1973: The residential portion of this building converts from apartments to condominiums.
Confidence votes 312. The Hancock Tower, from street level to the top of the building is 1,127 feet, however from street level to the tip of the spires is 1,500 feet.