Yes, you can paddle the canal in Western Maryland, but just barely! This is said to be the only significant segment with water outside the DC area.
I parked at Oldtown and rode the Potomac down to Town Creek Aqueduct to make the trip a loop. The river current is strong and there are a couple of easily-handled one-foot drops. Pull in on the left when you see a small trib with an arched structure. This is Town Creek.
Carry your boat up the bank and 100 yds along the path to where the canal water starts. (All put-ins and take-outs on this trip were muddy, weedy, and/or steep.) The canal here is a good 30 yards wide. Some trees have fallen in but none reach all the way across to block you. The C&O Rail to Trail is on your left; you can see Mile Marker 163 from the water. The right side is mostly a rock-and-pine wall. Most of this first 2-mile segment is covered by tiny floating lime-green circles (some sort of algae?) which do not affect your speed. Turtles peered at me before submerging.
Thunder began to crack, so I hustled to get to the first lock (#68). Pulled out and waited out a driving rainstorm on the covered porch of the lock-keeper's house (white clapboard and boarded up). There is hiker/biker camping here (I assume paddlers can use it too).
The water beyond this mid-point is mostly clogged with some kind of water lily that grows 2 feet above the water. As you plow through it, hundreds of tiny green insects (like aphids) drop into your lap. Thick as it is, it does not keep you from getting through. There is, however, an unanticipated carry around some sort of drainage construction project with pipes. Berms stretch across the water there. There is, however, also a drop-dead gorgeous section with clear water and a sheer rock wall on the right.
You hit Lock #69 and you are almost home. Carry that and there's another 200-yard water segment to Lock #70 and your final pull-out. Fishermen there wanted to know where I had put in, and said they didn't know boats were allowed in the canal.
Total trip: 2 hours down the river, 4 hours back up the canal. Despite carrying the locks and plowing through the water lilies...a success. Why? Because I never had to carry around a downed tree or due to lack of water. (Might be different in summer.)
Rural area. All facilities in Cumberland.
I paddle a 13' Necky Manitou.
Route 68 W to Exit 56/Flintstone. Right on Town Creek Rd to Oldtown.
National Park Service map of C&O Canal Natl Historical Park