I'd actually go so far as to say ALL riding areas have been closed to ATVs at this point. When I last rode Trevorton in 2011, that was still open to ride, but the writing was on the wall in 2013 that its days were numbered.
Your only option is to look into a private riding area, and these are usually outlaw trails that may very well cost you a fine if caught at some point. Potter County is full of these types of trails. I myself started out riding in White Haven, which offered well over 120 miles of outlaw trails.
2014 Wildcat Trail