The landlocked state of Pennsylvania and it's 12.4 million inhabitants (2007 est.) rank as the sixth largest populated state in the nation. Philadelphia and Pittsburgh are the states largest cities. As of 2007, Pennsylvania is the home of exactly one-tenth of all United States Fortune 500 companies. Alcoa, the largest producer of Aluminum in the nation (third largest in the world) holds it's corporate headquarters in Pittsburgh. Steel also plays an important role in the Pennsylvanian economy. Pennsylvania is the home of over 300 steel companies -- most notably U.S. Steel, the seventh largest steel producing company in the world.