If you want full hookups the only place is Cherry Hill in MD. If you can Live with Electric only and a water and dump station at the entrace then Bull Run is half the price and closer.
If you go to Cherry Hill you can use the Metro to get around. There is a stop for Arlington also. We did it last spring and it was great. Never had to worry about parking. Check out their site for more information. http://www.wmata.com/tripplanner/maps.cfm