It's been known as the Sears Tower since it opened in 1973, but the tallest building in the United States is set to change its name to Willis Tower.
The London-based insurance brokerage Willis Group Holdings will make the name change official during a ceremony in downtown Chicago on Thursday. Willis is leasing 140,000 square feet and moving 500 employees to the building. The new name isn't the only change, there is a $350 million greening effort underway and there are plans for a 50-story luxury hotel.
Some tourists have already ventured out on the new glass-bottomed enclosed balconies which opened earlier this month.
