Cherry Hill Park is the Closest Campground to Washington, DC :|: Cherry Hill Park
https://koa.com/find-a-koa/#%7B%22ma...3A%22%22%7D%7D
This is the area I grew up in. If the KOA link doesn't work just look up the KOA in Gambrills, Md.
The Cherry Hill Park is very close to the downtown DC area. I'll let you decide about that. It may have a kennel onsite. If not there are some near by.
Near the KOA in Gambrills is a Pet Resort. Located in Crownsville, Md. I have never been there but have heard nice things about it. Maybe 6 miles from campground.
Both of these campgrounds have bus shuttles to the DC sites. I recommend using that method. In the summer season the Cherry Hill Park has a very nice pool and water park. I have never been to the Gambrills park since it was in my neighborhood.
Sudsy