The skyscraper is thin, with 14,000 square feet (1,300 m2) of floor area on each story. In addition to the 58-story tower, there is a 125-foot (38-meter) 11-story tower on the complex's northeast corner. The total height of both towers is 204 feet (62 meters). There are no basement or ground floors at this location. The building was designed by O'Neil Ford Purdy Architects and constructed by Chicago's Durable Construction Co. It opened for business in 2002 after being delayed due to financial difficulties that followed the September 11 attacks. The firm also designed the Willis Tower (formerly known as the John Hancock Building), which is taller than the Millennium Tower. The Willis Tower is 324 feet (98 meters) tall. The top three floors of the Millennium Tower are named after women who have been influential in science and technology: Einstein, Newton, and Tesla. The bottom five floors are named after men who have made important contributions to science and technology: Boleyn, Faraday, Maxwell, Moissan, and Priestly. When it first opened its doors, the Millennium Tower was the tallest free-standing structure in the Western Hemisphere. This title has since been surpassed by the Sears Tower in Chicago but it remains a landmark in downtown Chicago. The building is owned by Millennium Partners LLC, which is headquartered in New York City.