Existing comment:
A Mountain Passage: Carved by an Ancient River:
Cumberland Gap is the result of four geologic features combining to create a natural opening through the Appalachian Mountains. Long ago, this land was flat, and Yellow Creek flowed south into Powell River. When the earth began to push up, creating the Cumberland Mountains, the Creek cut a notch. Beyond the notch lies Yellow Creek Valley and Middlesboro Basin, a large flat area. Together they form a passageway to The Narrows at Pine Mountain, which leads to the Bluegrass region of Kentucky. These natural features made it possible for pioneers and others to cross the Appalachian Mountains, which otherwise blocked westward passage.

"The Gap may be seen at a considerable distance, and there is no other, that I know of, except one about two miles North of it, which does not appear to be so low as the other."
-- Thomas Walker, 1750
Modify description