Campgrounds near Washington D.C.?

We've stayed at Cherry Hill Park in College Park MD a couple of times. It's close to the metro and even has a bus that stops there. It is very clean and well maintained, and they have a great staff. The sites aren't the largest, but I've been to cgs with tighter sites. You're near 496, so you will hear the constant drone of traffic, but you are in an urban area.