The Chesapeake & Ohio Canal National Historic Park has a 185 mile towpath, which is available for cycling. It runs from the Washington, D.C., area to Cumberland, Maryland, along the C&O Canal (which parallels the Potomac River). In Cumberland, it connects to the Great Allegheny Passage, which runs from there to Pittsburgh, Pennsylvania.
If the map has markers, click them for extra information. You can also double-click anywhere on the map to get driving directions to that point. Note:Trail routes shown are approximate! If you have a GPS trace of this trail, leave a comment below with your email address (which will not be published), and I'll contact you. Thanks!
Elevation profile of route: feet above sea level vs. distance traveled (approximate). Green marker on map above shows which end is designated as start of route.