The term "Alleghenian" primarily refers to the Allegheny Mountains, a major mountain range in the eastern United States. This range is part of the larger Appalachian Mountains and stretches across several states, including Pennsylvania, West Virginia, and Maryland. The Alleghenian region is known for its diverse ecosystems, rich natural resources, and scenic landscapes. In geology, "Alleghenian" also describes a specific period of mountain-building activity that occurred during the late Paleozoic Era. This event, known as the Alleghenian Orogeny, resulted in the formation of the Appalachian Mountains and significantly shaped the geology of the eastern United States.