Pittsburgh (/ˈpɪtsbɜːrɡ/ PITS-burg) is a city in the Commonwealth of Pennsylvania and the county seat of Allegheny County. It is the second-most populous city in Pennsylvania, behind Philadelphia, and 68th-largest city in the U.S. with a population of 302,971 as of the 2020 census. The city anchors the Pittsburgh metropolitan area of Western Pennsylvania; its population of 2.37 million is the largest in both the Ohio Valley and Appalachia, the second-largest in Pennsylvania, and the 27th-largest in the U.S. It is the principal city of the greater Pittsburgh–New Castle–Weirton combined statistical area that extends into Ohio and West Virginia.