Pittsburgh ( PITS-burg) is a city in the state of Pennsylvania in the United States and the county seat of Allegheny County. A population of 302,971 residents live within the city limits as of the 2020 US Census, making it the 68th-largest city in the U.S. and the second-most populous city in Pennsylvania, behind Philadelphia. The Pittsburgh metropolitan area is the anchor 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.