In 1969 Sears, then employing about 350,000 people, needed a single headquarters for 7,000 Chicago staff. Rejecting a suburban campus, the company had the law firm Arnstein, Gluck, Weitzenfeld & Minow quietly assemble a site on the western edge of the Loop using 90 day option contracts, securing 15 buildings from a block with over 100 owners, then paid the city 2.7 million dollars to close a block of Quincy Street. Architect Bruce Graham and structural engineer Fazlur Rahman Khan of Skidmore, Owings & Merrill designed a bundle of nine 75 foot square tubes, supposedly inspired by staggered cigarettes, that dropped off at the 50th, 66th, and 90th floors to break up wind vortices and create smaller rentable upper floors. Construction from 1970 used 201 caissons, a concrete plant in the basement, and electric current run through the steel to fight winter cold.

Suburbs including Skokie, Northbrook, and Deerfield sued to cap the tower at 67 stories over blocked TV signals, but a judge ruled there is no right to perfect reception, and Sears paid 5 million dollars to move station antennas to the roof. The tower topped out in May 1973 as the world’s tallest building, but by late 1974 Sears was laying off 500 workers there, and in 1995 it moved to Hoffman Estates. On July 16, 2009, Willis Group Holdings, leasing about 140,000 square feet, got the naming rights free, and Chicagoans refused to go along.

• The top can sway up to seven inches in high winds and return to center in just over seven seconds
• Time magazine ranked the Willis renaming among the 10 worst corporate name changes, alongside anger over Marshall Field’s becoming Macy’s
• Blackstone bought the tower in 2015 for 1.3 billion dollars and spent half a billion on upgrades including the Catalog retail complex
• The 103rd floor Skydeck and its glass Ledge boxes draw 1.7 million visitors a year
• Dan Goodwin climbed it in a homemade Spider-Man suit in 1981, and Alain Robert climbed it barehanded through fog in 1999