The Natural Tunnel, which is up to 200 feet (61 m) wide and 80 feet (24 m) high,[1] began to form more than a million years ago when groundwater bearing carbonic acid percolated through crevices and slowly dissolved limestone and dolomite bedrock.

A small river, which is now called Stock Creek, was diverted underground and it continued to erode the tunnel over many millennia.

A popular legend tells of a Cherokee maiden and a Shawnee warrior who had been forbidden to marry by their respective tribes, jumped to their deaths from the highest pinnacle above the Natural Tunnel.

The South Atlantic and Ohio railroad constructed tracks through the Natural Tunnel in 1893,[5] and the first train passed through the following year.

The railway originally carried passenger trains; today, the line is still open but now operated by Norfolk Southern, also used under trackage rights by CSX, and is only used to transport coal.