Authorities say the 19-year-old women were sitting on the edge of the bridge, enjoying one last summer night before heading back to college, when nearly two dozen railroad cars flipped over.
Their bodies were found buried under coal.
Some rail cars also fell over the bridge, hitting cars below and spilling coal everywhere.
Investigators were still trying to figure out what caused the derailment. Witnesses heard squealing brakes and a thunderous crash around midnight Monday.
The two train operators were not hurt.
The victims were identified as Elizabeth Conway Nass, a student at James Madison University in Virginia and Rose Louese Mayr, a nursing student at the University of Delaware.
The Associated Press contributed to this report.