Pittsburgh is a city in Allegheny County, Pennsylvania, United States, and its county seat. Located in southwestern Pennsylvania where the Allegheny and Monongahela Rivers meet to form the Ohio River, it had a population of 302,971 at the 2020 census, making it the second-most populous city in Pennsylvania after Philadelphia. The Pittsburgh metropolitan area has over 2.43 million people, making it the largest in the Ohio Valley and Appalachia, the second-largest in Pennsylvania, and the 28th-largest in the U.S. The greater Pittsburgh–Weirton–Steubenville combined statistical area includes parts of Ohio and West Virginia.