Blue Knob was thought to be the highest mountain in Pennsylvania until 1921, when the U.S. Geological Survey determined a summit of was higher (later named Mount Davis). In the 1950s the summit was cleared of vegetation and was the location of Claysburg Air Force Station until it was deactivated in 1961. Shortly afterward the Blue Knob Ski area was developed. Signs from the former station remain on the summit, and one building remains as a ski lodge. Ski lifts, a ski lodge and a couple of maintenance structures occupy the broad summit of Blue Knob, and a few ski chalets are downhill of the bald summit.