Rivnuts from Homestead, PA on 7/15/2021 8:19:55 PM:
Other than the 24 miles of the paved Western Maryland Rail Trail (WMRT) that parallels the C&O and the couple of miles of the repaired trail around Big Slackwater the balance of the C&O Towpath is crushed stone, fine gravel and hard packed earth. Of the unpaved length, there is a 40+ mile section from Shepherdstown to Edwards Ferry that has been improved with new, smooth, free draining crushed gravel in recent years. This is a good riding surface under most conditions.
If you leave the C&O and take the Capital Crescent Trail from Fletchers Boathouse on into Georgetown DC that is another 3-miles of pavement.
The 44-mile section between Cumberland and Little Orleans is generally hard packed earth (when dry) or puddles and mud (when wet).