Architecture of Chicago a new structural system of framed tubes in skyscraper design and construction. The first building to apply the tube-frame construction was the DeWitt-Chestnut Apartment Building which Khan designed and was completed in Chicago by 1966. This laid the foundations for the tube structures of many other later skyscrapers, including his own constructions of the John Hancock Center and Willis Tower (then named the Sears Tower) in Chicago and can be seen in the construction of the World Trade Center, Petronas Towers, Jin Mao Building, and most other supertall skyscrapers since the 1960s. Willis Tower would be the world's tallest building
Elgin Tower Building 1999 to showcase its architectural merit. Stickling died later that year, but his benefactors transferred the building to the William R. Stickling Charitable Foundation, who currently maintain the building. An addition was built in 1999 to house, rent-free, the Downtown Neighborhood Association, who intend to revitalize the downtown area. The tower was added to the National Register of Historic Places on May 22, 2002. The Elgin Tower Building is located at 100 E. Chicago St. in Elgin, between Douglas and N. Grove Avenues. This area has historically been known as Fountain Square, generally accepted as the downtown area of Elgin.