 In the southern half of the state, the AT passes through Caledonia State Park, Michaux State Forest, and Pine Grove Furnace State Park (the actual midpoint of the AT was slightly moved and is now over just under a half-mile west of PGF State Park and is marked by a "Midpoint" sign).These areas in south central Pennsylvania are the northernmost portions of the Blue Ridge Mountains, which are geologically distinct from the Ridge and Valley section further north.The two parts are separated by the broad Cumberland Valley, where the trail has a change of scenery, crossing many farms and large highways.