A Norfolk Southern "intermodal" train crosses the Little Conemaugh River just west of South Fork, PA. This section of the Pennsylvania Railroad follows the grade of the Allegheny Portage Railroad, originally part of the Mainline of Public Works that carried canal boats over the Allegheny Mountains. The original "Big Viaduct" was a single arch bridge and was destroyed by the Johnstown Flood in 1889. PRR rebuilt the bridge following the Flood as a two arch span.
