This is a pass through the Appalachian Mountains. It’s located at almost the exact point where Kentucky, Tennessee, and West Virginia come together.
It is depressed between 600 and 900 feet from the peaks on either side of it. It used to have a highway, but that was dangerous, so a tunnel under the gap was opened in 1996. The gap currently contains a national park.
It was named for the nearby Cumberland River, which was named for the Duke of Cumberland, in the 1700s.
Why I Looked It Up
I kept listening to the song Wagon Wheel by Darius Rucker (which is a cover of the Bob Dylan original from 1973). There’s a lyric that goes:
Walkin’ to the south out of Roanoke
I caught a trucker out of Philly had a nice long toke
But he’s a-heading west from the Cumberland gap
To Johnson City, Tennessee