The Pennsylvania Railroad Stone Bridge spanning the Conemaugh River at Johnstown was built in 1887 — just two years before the flood — and became one of the most significant and haunting sites of the disaster. When the flood wave hit, the massive arched viaduct acted as a dam, catching the debris carried down the valley and piling it up against the bridge's six stone arches.
The debris pile — estimated to stretch across some 30 acres — caught fire, possibly ignited by overturned stoves or lanterns in the wreckage, and burned for three days. People trapped alive in the debris died in the flames. The bridge itself survived structurally and is still in active railroad use today, making it one of the few flood-era structures still functioning in its original purpose. It can be viewed from the riverbank. A historical marker near the site explains what happened here.