500 West Madison or also Citigroup Center is a 42 story, 588-foot skyscraper in Chicago, Illinois. 500 W. Madison was designed by the architecture firm Murphy/Jahn in a late modernist style. The building, previously named the Northwestern Atrium Center, was constructed between 1984 and 1987 on the air rights obtained by the destruction of the headhouse of the 1911 North Western Station. Citigroup Center contains retail shopping and offices, and is connected to the platforms of the Ogilvie Transportation Center (which unofficially continues to be called Northwestern Station) and thousands of Metra commuters use the facility every day. Orbitz Worldwide (NYSE: OWW) maintains its worldwide headquarters on three floors of the Citigroup Center.