http://fragis.frasafety.net/GISFRASafety/
The FRA's GIS system. Rail maps of every rail line in existance, and a ton of abandoned ones.
I found some inaccuracies, as far as some lines active that were abandoned, and vice versa, and some lines abandoned very long ago that did not even show up, but this is awesome I think...
I'm guessing the abandoned lines that aren't shown were abandoned before the FRA was formed in 1966. And that was quite a few here in VA.
Guess not then. My first thought was it only showed abandoned RoWs still owned by a railroad or owned by the state (e.g., rail trail), but I found a few examples to the contrary.
If you're into history you might like the scans I have of some railroad atlas maps from the 1910s and 20s. They show the eastern network pretty much at its fullest extent. It was an eye opener to see some of the places the rails used to run in my neck of the woods.
Anyway, the FRA GIS is pretty impressive. Definitely bookmarking it.