I’ve been wanting to do this but I don’t know the route. Should I just check the rail trail site or do you know of a better resource?
The Great Allegheny Passage (GAP) [2] connects Cumberland, MD and Pittsburgh, PA:
For maps, I recommend the two available from the Allegheny Trail Alliance (ATA)'s website at:
https://gaptrail.org/explore/printable-maps
Also, there is a mobile app for the C&O Canal Towpath from the C&O Canal Trust (the official nonprofit partner of the C&O Canal National Historical Park)
https://www.canaltrust.org/plan/explorer-mobile-app/
[1]: https://www.canaltrust.org/plan/co-canal-towpath/
[2]: https://en.wikipedia.org/wiki/Great_Allegheny_Passage