Pittsburgh (/ˈpɪtsbərɡ/ pits-burg) is the second-largest city in the U.S. state of Pennsylvania with a population of 305,842 and the county seat of Allegheny County. The Combined Statistical Area (CSA) population of 2,659,937 is the largest in both the Ohio Valley and Appalachia and the 20th-largest in the U.S. Pittsburgh is known as both "the Steel City" for its more than 300 steel-related businesses, as well as "the City of Bridges" for its 446 bridges. The city features 30 skyscrapers, 2 inclines, a pre-revolutionary fortification and the source of the Ohio River at the confluence of the Monongahela and Allegheny Rivers. This vital link of the Atlantic coast andMidwest through the mineral-rich Alleghenies made the area coveted by the French and British Empires, Virginia,Whiskey Rebels, Civil War raiders and media networks.
Aside from steel, Pittsburgh has led innovations in aluminum, glass, shipbuilding, petroleum, foods, sports,transportation, computing, autos, and electronics. This creative wealth placed Pittsburgh behind only New Yorkand Chicago in corporate headquarters employment, second to New York in bank assets and with the most U.S. stockholders per capita for much of the 20th century. America's 1980s deindustrialization laid off area blue-collar workers and thousands of downtown white-collar workers after multi-billion-dollar corporate raids relocated the longtime Pittsburgh-based world headquarters of Gulf Oil, Sunbeam, Rockwell and Westinghouse. This status as a global industry center, its melting pot of immigrant workers, and top-10 rank among the largest U.S. cities until 1950 and metro areas until 1980 left the area with renowned museums, medical centers, parks,research centers, libraries, a vibrantly diverse cultural district and the most bars per capita in the U.S.