Pennsylvania has of the trail. The trail extends from the Pennsylvania - Maryland line at Pen Mar, a tiny town straddling the state line, to the Delaware Water Gap, at the Pennsylvania - New Jersey border. The Susquehanna River is generally considered the dividing line between the northern and southern sections of the Pennsylvania AT. South of the Susquehanna, the trail passes through Pine Grove Furnace State Park. The Pennsylvania section of the trail north of the Susquehanna, from Duncannon until the Delaware Water Gap, is noted for its eroded and rocky terrain which can slow hiking.