Over 100 years ago, there was a railroad that went from Oakland, Maine to the tourist resort at Kineo, on Moosehead lake. It was called the "Somerset Railroad". The train station in Solon (where I live) closed in 1935, and the last service was to Bingham in 1975. But the right-of-way still exists as a "rail trail" with at least 50 geocaches between Solon and Lake Moxie - about 30 miles north. (and there more north of there...)
This history of the Somerset Railroad is fascinating, and is documented in a Book from DownEast Books of Camden, "The Old Somerset Railroad".
This is such a great ride, both for geocaching and just getting into the scenic Maine woods. I plan on adding to this thread with pictures and a "caches along a route" listing. The trail is accessible by bicycle, ATV and snowmobile. The 6-mile stretch between Solon and Bingham (6 miles, 23 caches, along the Kennebec River)) can also be walked easily. (If you want to drop your car at one end, I might be persuaded to drive you back to the starting point...)