JimK-NY wrote:
I have visited Maryland locations several times and never had any cost issues. State Parks including great areas like Cunningham Falls (Thurmont) and Patapsco Valley are around $20/night. Other choices can be found that are much cheaper. I have stayed at the Maryland House rest area several times for no cost. I visited Baltimore and stayed at the Walmart supercenter....both the one in town and the one on the north side of Baltimore....again for no cost. I have visited Washington, D.C., numerous times. I usually stay at Evergreen National Park, which is next to the beltway, about 2 miles from the metro station and a quick ride into the heart of the city. Senior cost is $8, full fee is $16.
I am still guessing the OP has a big rig that needs lots of space and hookup fees. RV parks, especially on the east or west coasts can get expensive...way over $30/night.
The OP was inquiring about a site for a month. The state parks have a two-week limit and you wouldn't stay at a WalMart of rest area for a month...and least you shouldn't.
I was hoping the OP would return to let us know what he found out.