Another one, a virtual unknown, bears mention in this thread. Diamond Match Co.'s narrow gauge Burnt Cabin Railroad in the Idaho panhandle; the last narrow-gauge logging line in the state. Isolated from any rail connection, it ran to a landing on Priest Lake from whence the logs traveled by raft. The locomotives and rolling stock got there originally by skidding across the frozen surface of the lake. This line did not use steam, wasn't exactly "dieselized" either - it used Plymouth gas-mechanical lokies.
To add slightly to Lon's post; The St. Marie's
River railroad (owned by Potlatch) is indeed still operating, although I believe it hauls more mill waste and and finished lumber than logs these days. I have heard but cannot confirm that the Camas Prairie's Orofino line is still in place, but out of service.
J