Recommend a riverside campground within 3-4 hours of Balt MD

I second Andy Guest/Shenandoah River State Park in Virginia.

I will also suggest Janes Island State Park in Maryland. While not on a river - it is on the bay - they have some great water trails. One can kayak to a deserted beach in the Chesapeake Bay and enjoy the day.

Point Lookout State Park is another great kayaking/canoeing park in Maryland with a lake, the Potomac River, and the Chesapeake Bay available. The campground has full hook up sites in the woods or electric sites on the water. An excellent place in October...

And don't forget Assateague - canoeing/kayaking is great bayside, though not a river.

Check out Brunswick Family Campground, on the Potomac River. Brunswick, MD

Wonderful, mild water section of beauty. Great fishing, we see Bald Eagles regularly. We stayed at the campground, put our kayaks in and had a shuttle car at Point of Rocks for at the end of the day. The outfitter that runs the campground offers many boat rentals and trip options. Also a shuttle service if you don't have a second vehicle to do your own shuttle.

Many places to stop and fish along the route, eat lunch and swim.

Campground is pretty good but if a recent flood has occurred the ground will be damp. I believe there are 2 Trains go by the campground at night,so bring earplugs if you are a light sleeper.

Brunswick campground, on the potomac. KOA Hagerstown on a small creek.
bumpy

Thanks for replies! More are welcome. :-)

Have my own canoe...

There are a number of canoe companies along the Shenandoah River between Front Royal and Luray, VA. I canoed from Bentonville, VA to Front Royal years ago and had a nice time. Now, as far as campgrounds go, from what I researched, most of the canoe companies only have tent and cabin camping facilities. IMO, the best campgrounds in that area are either KOA Luray or Shenandoah River/Andy Guest State Park near Bentonville. You can always drive your truck to the canoe places. Good luck and have fun.

I recommend VA State Parks
If you're willing to drive one hour more, HUNGRY MOTHER SP in Marion, VA is beautiful and on a river.
http://www.dcr.virginia.gov/state-parks/hungry-mother.shtml#cabins_camping

Claytor Lake SP is about ten minutes closer to you. Both of these allow canoe kayaking and have beautiful parks.
http://www.dcr.virginia.gov/state-parks/claytor-lake.shtml#cabins_camping