Norfolk Southern freight heads south near Burnside, KY on the“Rat Hole,” a section of the line from Cincinnati to Chattanooga.

This railroad, first built 1869-1880, was extensively rebuilt in 1959-1963, reducing curves, flattening grades, and replacing tunnels with huge rock cuts like this one — it’s a rare example of large scale post-WWII engineering on the US freight rail system.

It’s not easy to build through country like this.

The line is also special in another way — it’s owned by the City of Cincinnati, which originally financed and built it, and leased to NS. At 337 miles, it’s by far the biggest municipal rail line in the US.