As others have said Cherry Glenn, I’d also recommend Trout Run it’s just north of Williamsport and can be reached in about three hours. Camp at Sheshequin Campground which is in a bit of a valley surrounded by mountains to block out the lights from Williamsport. On a clear night you should be able to see the Milky Way along the river behind the campground. Rock Run is nearby and has a lot of great trails to hike and swimming holes.