The Allegheny Mountains form the boundary between the Appalachian Mountains and the Great Plains.

The Allegheny Mountains, part of the larger Appalachian range, serve as a geographical divide between the Appalachian Mountains to the east and the Great Plains to the west. This range stretches across several states, including Pennsylvania, West Virginia, and Maryland. The Alleghenies are known for their rugged terrain, dense forests, and rich biodiversity. They act as a natural barrier, marking the transition from the Appalachian region's mountainous landscapes to the flatter, more expansive plains of the Midwest. The Allegheny Mountains are also significant for their historical role in early American development, as they were key in shaping transportation routes and settlement patterns.