An item that ran in the Chicago Tribune in 1969:
The newest infant resident of the Hancock building won’t have any trouble remembering where he lives when he gets older. He is Mark Hancock Thorne who was named yesterday by his parents Mark and Cindy Thorne, who moved into the building two months ago. Young Mr. Thorne was born Wednesday in Wesley Memorial Hospital.
The Thornes would have been among the very first residents of the super-tall skyscraper, which had been completed earlier the same year.
Source: “Baby Named for Building.” Chicago Tribune 21 Jun. 1969: N3.
P.S. The name of the building was changed from “The John Hancock Center” to 875 North Michigan Avenue in 2018.