This is the Appalachian Trail Museum in Pine Grove Furnace State Park, Pennsylvania. It's brand new, having opened in the spring of 2010. The exhibits are primarily about the early, pioneer through-hikers, such as Earl Shaffer and Grandma Gatewood. The museum is free, although donations are appreciated.
The museum is in this location because it is almost at the exact midpoint of the Appalachian Trail. Due to constant re-routings, the midpoint moves around a bit from one year to the next, but it is always just a few miles north of the park.
Pine Grove Furnace State Park is located on PA Route 233, about twenty miles north of US Route 30 (the Lincoln Highway)