Heading to Camden Yards, need advise on campground

Cherry Hill.

If DC is in the mix. Cherry Hill is your best bet. Very convenient to DC attractions. Close enough to Baltimore to see the Orioles....I mean White Sox...LOL

The intent is to visit D.C. by day and Camden Yards by night.

Cherry Hill is the best option if you're going to do the DC tourist stuff during the day. Very convenient to the METRO (subway) system. About 27 miles to Camden Yards, but you'll also be dealing with some of the evening rush hour commute, too. Sounds like a long day, but doable. Enjoy!

Coming from North Carolina.

The intent is to visit D.C. by day and Camden Yards by night.

Are you traveling in from the west?
Cherry HIll is doable. But it is a little far. Not too bad if you want to tour DC while in the area.
Patapsco state park has a decent CG and is pretty close to the Camden Yards.
Millersville KOA is a decent option as well.
For the most part you will want to drive in vs. public transportation.
There is a car rental about a 1/2 mile from Patapsco state park.

Two other campgrounds in the area are Bar Harbor RV Park in Abingdon, Md

areBar Harbor RV Park

and Merry Meadows in Freeland, Md.

Merry Meadows

I have never been to Bar Harbor, but they advertise that they are the closest campground to the Inner Harbor. Close to I-95.
I camped at Merry Meadows before it changed hands and it was a nice campground. Don't know how it is now.

There are not a lot of campgrounds in the Baltimore area.

Anyone ever stay at Cherry Hill?

and thanks bumpy, I will check out the KOA you mentioned.

KOA between annapolis and baltimore would be one option.
bumpy