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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.
John Hancock Center. For the tower in Boston, see John Hancock Tower. The John Hancock Center is a 100-story, 1,128-foot (343.7 m) supertall skyscraper at 875 North Michigan Avenue, Chicago, Illinois, United States. It was constructed under the supervision of Skidmore, Owings and Merrill, with chief designer Bruce Graham and structural engineer Fazlur Khan.