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.
Pittsburgh is known as "the Steel City" for its dominant role in the history of the U.S. steel industry.