Pedestrians walk past the entrance to the old Sears Tower in Chicago after it was officially renamed Willis Tower during a ceremony Thursday, July 16, 2009. The country's tallest building and one of the world's iconic skyscrapers was renamed after London-based insurance brokerage Willis Group Holdings as part of its deal to lease 140,000 square feet of space in the tower.
By Mark Scarp, contributing columnist
By Jerry Brown, contributing columnist
Guest Commentary by Bill Richardson
Guest Commentary by Shawn Thiele
By Mark Heller, Tribune