Hi Amanda. Pennsylvania is a big state! If you're traveling down I-81, there isn't a whole lot near the highway. At least in the south end of the state.
A bit north/northwest of Harrisburg is Bald Eagle State Forest, which has quite a bit. Take a look through
https://www.overlandbound.com/forums/threads/pennsylvania-bald-eagle-state-forest.22173/ for lots of info, and I think some tracks posted by
@DevilDodge .
Down here closer to Maryland is Michaux State Forest, with some trails and as I understand it has no remote camping.
Keep in mind that it is hunting season here, so some roads are open only for that purpose, and hunters are taking over the forests. Also, due to the hurricane remnants and other weather, it will be very muddy and potentially challenging in a different way for a full size rig.
Safe travels! If I can be of further assistance, please reach out. DevilDodge is an outstanding resource for PA also. I look forward to meeting you on Saturday.
Mike