This route doesn't actually begin in Sharpsburg, but just outside (off the MD34) and meanders nicely along the river.
One doesn't need to ride the whole thing. Too many towns. However, the Bear Mountain area is Jolly Good. Not too shabby from Bear Mountain to West Point, NY. Quik trip: Take the Palisades Parkway to Bear Mountain, then 9W to WestPoint. No matter what, go into the park and ride to the top. You can see new York City on a clear day.
Don't forget to venture off around Upper Greenwood Lake. Watch out for kids, horseback riders, and road construction. Try not to go on the weekend for more open road access