How did an ancient meteor impact help America spread westward?

The Appalachian Mountains aren't the largest mountains in the United States, but they still present lots of rugged topography which can present an obstacle to travel. Native peoples and even wildlife learned to make use natural gaps and other landforms that made travel practical. European settlers followed suit, and the famous Cumberland Gap was one of the most significant landforms that allowed reasonable passage across some of Appalachia's roughest topography. Interestingly, Cumberland Gap was only good because it opened onto the Middlesboro Impact Structure, the product of an ancient meteor impact. The Middlesboro Structure, in turn, is located next to Rocky Face, a conveniently placed ridge on a minor fault line. Together, these geologic features created a unique path through an otherwise nearly impassable area. This video explains their development with lots of map images and diagrams.