Most of the spots I use to wheel are now banned and the police enforce this. I have awesome Power Line trails all around Southern MD, but are now off limits, damn young kids hurting themselves screwed that up here. Wheeling in Maryland is hard to find due to law restrictions. I would consider looking into PA or WV/Vir. Some private places in MD charge to go there, which is crazy. I like PA myself. Western Maryland has a couple of trails for trucks also, but nothing to fun.

Paragon Adventure Park (PA)
Rausche Creek (PA)
Stateline (MD)
Tellico (NC)
Shoe Creek (VA)
Crozet (VA)
George Washington National Forest (VA)
Gore (VA) Home of all Big Dogs events
Uhwarries National Forest (NC)