nothing legal. MD sucks for ORV stuff. there used to be a mud bog competition up near taneytown on certain saturdays. not sure if it still happens or not.
if you are looking for ORV parks, the closest thing is Rausch Creek in PA. I used to go wheeling there with my jeep. awesome place, but more for rock crawling, not really a place geared towards mudding.
2011 F150 SCAB 4x4 FauX4
Oxford White STX 5.0