Washington DC area

Earlyish Sept is an awesome time to go there. We've always stayed at Cherry Hill. Been there a couple times and yet we still either see the same sights or try to hit some new ones. A, IMO a MUST see every time is the changing of the guard at Arlington. Don't carry a pocket knife w/ you as you have to pass thru a metal detector for 99% of places. Look into taking a Grey Line tour. Have fun.

Cherry Hill Park is your only reasonable option. Book a site close to the front, as that is where the bus stop is that will take you to the train. After a day of sight seeing and walking until you think your feet are falling off, the last thing you want to do is walk another mile back to your camper!

Cherry hill is a good option, though not exactly inexpensive (but that's not to say overpriced; they offer a lot and charge correspondingly).

Not far from them there's Greenbelt National Park, which is not expensive but has very few ammenities (no hookups, typical rustic public campground) but lots of sites and a reasonable walk of maybe a mile and a half to the nearest Metro station.

East of the city there's Lake Farifax county park, which offers intermediate ammenities (hookups, etc.) and likewise is not too distant from a Metro station. I think all three campgrounds are around a mile or two walking from their respective nearest Metro stations, or a bit farther by car on the roads.

As bgum says, you'll be there a very long time to begin to see everything.

Good luck, we lived there for 4 years and never saw it all.

We did the same as you are planning 2 years ago and stayed at Cherry Hill. It’s a piece out of town but the shuttle to the train station was convenient. The campground is nice and clean and the pizza and ice cream by the pool canteen is pretty good. The sites near the front are pretty wide open with no privacy but there are sites near the back of the grounds that are treed and have some shade and more privacy. There is a resident dog walker that does a great job keeping the pooches happy too.

Cherry Hill is most likely the best choice for you. Close to the rapid transit and even has a bus that runs to the station. If yu are eligible for military FamCamps, we found Camp Meade RV Park to be a very nice alternative though it is about a twenty minute drive to the station.