The Sears Tower, one of the world's iconic skyscrapers and the tallest building in the U.S., was renamed the Willis Tower  in a downtown ceremony, marking a new chapter in the history of the giant edifice that has dominated the Chicago skyline for nearly four decades. The 110-story skyscraper may officially have a new name for the first time since its 1973 opening, but many Chicago residents said they weren't buying it...more.