Railroad Archives Online
- CollectionE0477 - BNSF Maps, Drawings and Records Collection
- Series003 - Great Northern Railway Company (U.S.)
- Subseries Level 1009 - Engineering Records
- Subseries Level 3005 - Signals
- ItemEBP0437 - Signals Technical Drawing, 1901
- ItemEBP1860 - Great Northern Track Technical Drawing, 1907
- ItemEBP2618 - Northern Pacific Signal Technical Drawing, 1902
- ItemEBP3610 - Northern Pacific Signal Technical Drawing, 1898
- ItemEBP4365 - Great Northern Signal Technical Drawing, 1912
- 3 more...