Railroad Archives Online
- CollectionD0288 - Terence Wahl Collection
- Series003 - Great Northern Railway Company (U.S.)
- Subseries Level 1014 - Photographs
- Subseries Level 2003 - Railroads--Buildings and Structures
- Subseries Level 3005 - Signals
- ItemTRWahl0275 - Great Northern Block Signal, Bellingham, Washington, undated
- ItemTRWahl0276 - Great Northern Block Signals, Bellingham, Washington, undated
- ItemTRWahl1053 - Great Northern Block Signal, Bellingham, Washington, undated
- ItemTRWahl1054 - Great Northern Block Signal, Bellingham, Washington, undated
- ItemTRWahl1056 - Great Northern Speed Limit Sign, Bellingham, Washington, undated