Best RV parks near Washington, D.C. and New York City?

I haven't stayed at Cherry Hill, but as long-time Washington, DC area resident, I can vouch for the importance of having access to public transportation. Even if you have a toad, you probably don't want to drive into DC. You'll pay ~ $15 to park (not that close to the Mall) and endure heavy and possibly confusing traffic. Cherry Hill's advantage is that it is a quick bus trip to the METRO station. Most other area campgrounds don't have that, and if you're driving to METRO, you better get a real early start because the commuters fill the parking lots pretty early. That said, there may be a new option for anyone that wants to stay on the Virginia side. The Wiehle-Reston East Metro Station on the newly opened Silver Line METRO extension appears to be within walking distance of Lake Fairfax Park. I think it requires a shortcut through the woods - not sure how good the path is or whether there are any busses, but the Park Office could probably supply that info. Might be worth considering if you have a reason to be in Virginia, otherwise I'd stick with Cherry Hill.