Mountain chain in the eastern United States, extending from the valley of the St. Lawrence River in Quebec, Canada, to the coastal plain of the Gulf of Mexico in Alabama.
Note: Location of the Appalachian Trail, the world's longest continuous hiking path. It extends over two thousand miles from Maine to Georgia.
Note: Historically, the Appalachian Mountains were a barrier to early western expansion. In the early 1840s, railroads began to transport settlers across the mountains, permitting access to the frontier.