I'm going to guess the summit between Lloydsville & Blandburg, on the former Bells Gap Railroad, altitude 2,240 feet. That seems to beat the PRR's other crossings of the Allegheny Front (Gallitzin, Tyrone & Clearfield through Emigh's Gap, Bellefonte & Snow-Shoe at Rhoads) and the summit on the Kinzua Ry. at Marshburg.