Railroad Archives Online
- CollectionD0036 - George Werkema Collection
- Series003 - Great Northern Railway Company (U.S.)
- Subseries Level 1014 - Photographs
- Subseries Level 2003 - Railroads--Buildings and Structures
- Subseries Level 3007 - Tunnels
- Itemimg1117 - Great Northern Tunnel at Scenic, Washington, 1999
- Itemimg1120 - Great Northern Tunnel at Scenic, Washington, 1982
- Itemimg1121 - Great Northern Tunnel at Berne, Washington, 1982
- Itemimg1122 - Great Northern Tunnel at Berne, Washington, 1982
- Itemimg1123 - Great Northern Tunnel at Berne, Washington, 1982
- Itemimg1124 - Great Northern Tunnel at Scenic, Washington, 1982
- Itemimg1125 - Great Northern Tunnel at Tye, Washington, 1968
- Itemimg1126 - Great Northern Tunnel at Seattle, Washington, 1977
- 2 more...