This is a shot in the dark as your OP does not mention what kind of CG you are looking for or the purpose of your stay.
1. Clarksburg, MD Little Bennett Regional Park, exit 18 on I270, 301-972-9222 I have not stayed here.
2. A few mile to the East is Cherry Hill CG. This is a full service CG. 301-937-7116. I have stayed here many times and highly recommend it. If you are there to tour D.C., this CG is a good choice.
3. A few miles to the SW there is Lake Fairfax Park, Reston, VA. 703-471-5415. I have never stay at this park.
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