It is the simplest of rigs: monofilament line tied to a modest swivel, then attach a trim bobber 6 inches above it and put an Eagle Claw snelled hook (size 6) on. Put a worm on (put the hook through both ends and the middle), and cast and watch.
I have had the following fish strike this rig and bait: bluegill, sunfish, large-mouth bass, channel catfish, and a carp.
The map above shows where I have had success—but don’t feel obliged to try only there. Fish run through the canal, which runs from Pennsylvania to Washington, DC. Wherever one finds a bridge or a fallen tree or brush in the water—those are good places to cast your bait.
One question I sometimes get is, “How can fish be in the canal?” Simple: the canal connects to Rock Creek and the Potomac River—so the fish in the latter two end up in the canal.
Bike/walking/running trails (former towpaths) run along the canal—so if you fish one spot and find it wanting, move along!