Railroad Archives Online
- FondsE0480 - Great Northern Railway Historical Society Miscellaneous Collection
- Seri003 - Great Northern Railway Company (U.S.)
- Subseri012 - Cartographic materials
- 001 - Railroads - Right of Way
- Item1935GNInterlockings - Map of Interlockings on the Great Northern Railway, Showing Location, Type, Number of Levers, and Ownership, 1935
- Item1935GNSignalChart - Map of Signal Systems on the Great Northern Railway Including System Type Where Present, 1935