Interesting! thanks for sharing. The map of all the abandoned rail roads in the US. is interesting. So much history along some of those railroads many of which were built in the 1800's. Its amazing how they built railroad bridges, tunnels through mountains, and carved out mountain sides to lay a rail road bed with the little technology they had then. Lots of men putting in lots of hours of hard work. Just getting the materials to some of those remote areas would have been a task in its self. Pa is one of the states that have lots of abandoned rail roads that have been converted into rail trails, which since I retired have taken advantage of riding a bike on them. Its really interesting riding them and passing through some of the old coal mining towns, logging towns towns that produced steel, mined iron ore, and shipped oil by rail.
One of the greatest feats of engineering I have seen along many of these rail trails is the Two tunnels built in the early 1900's along the Allegheny river. One is the Rockland tunnel, which is 2900 feet long, and the other is the Kennerdale tunnel that is 3,350 feet long. Both tunnels were built to shorten the route, by going through a mountain. Both can be rode through by bike or by walking.