The claim: Halfway between the District of Criminals and Baltimore. Data needed.
What it really is: Fort George G. Meade Army base is the home to the National Security Agency, the United States Cyber Command, and the Defense Courier Service (all of which I imagine the sovereign citizens movement hates...) amongst other things.
There is also a lot of housing and even businesses around there as well. Also, while there are a bunch of large buildings in this area, none of them resemble prison camps.
The lack of information, combined with the fact that whomever made this claim didn't even know that several intelligence agencies were located here leads me to believe that this claim is bogus.