Railroad Archives Online
- CollectionD0059 - David Emerson Collection
- Series003 - Great Northern Railway Company (U.S.)
- Subseries Level 1014 - Photographs
- Subseries Level 2003 - Railroads--Buildings and Structures
- Subseries Level 3007 - Tunnels
- ItemDEGN201314042 - Great Northern First Cascade Tunnel, Washington State, 1900