Willis Tower new competition by retailing giants such as Kmart, Kohl's, and Walmart. The fortunes of Sears & Roebuck declined in the 1970s as the company lost market share; its management grew more cautious. Nor did the Sears Tower draw as many tenants as Sears had hoped. The tower stood half-vacant for a decade as a surplus of office space was erected in Chicago in the 1980s. In 1990, the law firm of Keck, Mahin & Cate decided to move out of its space in the Sears Tower and into a development that would become 77 West Wacker Drive, rebuffing Sears' attempts
Willis Tower unfinished World Trade Center to become the world's tallest building. The height was restricted by a limit imposed by the Federal Aviation Administration (FAA) to protect air traffic. The financing of the tower was provided by the Sears company. It was topped with two antennas to permit local television and radio broadcasts. Sears and the City of Chicago approved the design, and the first steel was put in place in April 1971. The structure was completed in May 1973. The construction cost about US$150 million at the time, equivalent to $ million in 2019. By comparison, Taipei 101, built in