City Landscapes — tallest-buildings: Willis Tower fka Sears Tower...
Sears Tower, Chicago
6 Interesting Facts about Willis Tower (Former Sears Tower) – The Tower Info
Central Park Tower Surpasses Chicago's Willis Tower On Way To Tallest Roof Height In Western Hemisphere - New York YIMBY
Sears Tower: A Building Book from the Chicago Architecture Foundation: Jay Pridmore, Chicago Architecture Foundation, Hedrich-Blessing: 9780764920219: Amazon.com: Books
File:Skyscrapercompare1.PNG - Wikimedia Commons
Willis Tower | Height & Facts | Britannica
One World Trade Center seizes U.S. height crown from Chicago's Willis Tower - MarketWatch