The Allegheny Portage Railroad was the first railroad constructed through the Allegheny Mountains in central Pennsylvania. It operated from 1834 to 1854 as the first transportation infrastructure through the gaps of the Allegheny that connected the midwest to the eastern seaboard across the barrier range of the Allegheny Front. Approximately 36 miles (58 km) long overall, both ends connected to the Pennsylvania Canal, and the system was primarily used as a portage railway, hauling river boats and barges over the divide between the Ohio and the Susquehanna Rivers. Today, the remains of the railroad are preserved within the Allegheny Portage Railroad National Historic Site operated by the National Park Service.

The Allegheny Front is the major southeast- or east-facing escarpment in the Allegheny Mountains in southern Pennsylvania, western Maryland, eastern West Virginia, and western Virginia. The Allegheny Front forms the boundary between the Ridge-and-Valley Appalachians to its east and the Appalachian Plateau to its west. The Front is closely associated with the Appalachian Mountains' Eastern Continental Divide, which in this area divides the waters of the Ohio/Mississippi river system, flowing to the Gulf of Mexico, from rivers flowing into Chesapeake Bay and from there into the Atlantic Ocean.