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
- 4 more...
- 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
- Itemimg1144 - Great Northern Tower at North Portal (Seattle, Washington), Washington, 1982
- Itemimg1145 - Great Northern Tower at North Portal (Seattle, Washington), Washington, 1982