Railroad Archives Online
- CollectionD0237A - Great Northern Railway Historical Society Cascade Division Collection
- Series003 - Great Northern Railway Company (U.S.)
- Subseries Level 1014 - Photographs
- Subseries Level 2003 - Railroads--Buildings and Structures
- Subseries Level 3010 - Miscellaneous Structures
- ItemGNRHSCD031 - Greenhouse near Monroe, Washington, circa 1925
- ItemGNRHSCD053 - Interlocking Status Panel at UD Tower, Seattle, Washington, undated
- ItemGNRHSCD054 - Interlocking Control Panel at UD Tower, Seattle, Washington, undated
- ItemGNRHSCD055 - Interlocking Manipulation Directions at UD Tower, Seattle, Washington, undated