Railroad Archives Online
- ArquivoD0237A - Great Northern Railway Historical Society Cascade Division Collection
- Série003 - Great Northern Railway Company (U.S.)
- Subsérie014 - Photographs
- 003 - Railroads--Buildings and Structures
- 010 - 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