That's an interesting concept for a ride. Might I suggest the Memorial Bridge and Chain Bridge as better crossings than the American Legion. Both have a good bit of character. The Memorial Bridge has Arlington National Cemetary on one side and Lincoln Memorial on the other and is a beautiful bridge from back when they built bridges as works of art not just transportation. Chain Bridge is in a really nice, wooded area of DC/VA and would be perfect access to the GW Parkway to continue north. The American Legion Bridge is, well, a modern day, rough, plain, etc. interstate bridge. START EARLY to miss DC traffic/tourists - like 7-730am.
White's Ferry is cool. Check schedules though. I know from experience they don't run if the ferry is frozen into the river (misguided mid-winter m/c excursion
)
Point of Rocks is nice and a popular m/c route. May also want to consider the crossing at Brunswick and also where US340 crosses at Harper's Ferry.
I'm sure there's plenty of folks on here with tons of experince on the roads. I don't know the policy on sharing routes
. My experience is you won't get really good roads with the good possibility of little traffic until you're at least north of Point of Rocks.
Send me a PM with your email address and I'll send you a google map of a route I rode recently with some nice roads.
And hey, you may as well take the ride all the way to the source!
http://en.wikipedia.org/wiki/Fairfax_Stone