Landmark opened in 1973 with original tenant Sears Roebuck & Co. CHICAGO, Illinois (CNN) -- Sears Tower is history. As of Thursday, the iconic Chicago, Illinois, skyscraper is now named Willis Tower.

More than 1.7 million people make their way to Willis Tower's Skydeck Chicago each year, and it's easy to see why. Occupying the 103rd floor – that's nine floors higher than 360 CHICAGO – of ...