Pittsburgh, Pennsylvania, was a thriving and important city during the American Civil War, and provided a significant source of personnel, war materiel, armament, ammunition, and supplies to the Union Army. Situated at the confluence of the Monongahela, Allegheny and Ohio rivers, Pittsburgh was an important transportation hub for both riverine and rail transport, as well as overland via its system of roads.

Pittsburgh is a city in the Commonwealth of Pennsylvania and the county seat of Allegheny County. It is the second-most populous city in Pennsylvania after Philadelphia and the 68th-most populous 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 2.457 million is the largest in both the Ohio Valley and Appalachia, the second-largest in Pennsylvania, the 7th-largest in the Mid-Atlantic region and the 26th-largest in the U.S. Pittsburgh is the principal city of the greater Pittsburgh–Weirton–Steubenville combined statistical area which includes parts of Ohio and West Virginia.