This tunnel, referred to in early N&W documents as “Tunnel 377”, was first known as the Coaldale tunnel, but is now officially (as the sign on the lintel says) the Elkhorn tunnel. Shown is the SE portal at 37.333022, -81.338904, about one mile as the crow flies, from the NW portal of the Coopers tunnel, across the Bluestone River. The tunnel is on the Flat Top Extension, which opened up a way to the Ohio River for the N&W. It was excavated between 1887-1888 and is 1.3 miles long.
Enjoying your blog, noticed this photo of the new Elkhorn tunnel. New Elkhorn tunnel replaced the single track old Coaldale tunnel which is close by to the north and slightly higher. Portals for that tunnel were buried. New Elkhorn was finished about 1950 and is 7101 feet in length. It originally had ventilating fans for blowing out the smoke from steam locomotives.
These guys knew how to bore a tunnel!