Railroad Archives Online
- CollectionD0063 - Walter W. Ainsworth Collection
- Series004 - Northern Pacific Railroad Company
- Subseries Level 1014 - Photographs
- Subseries Level 2001 - Railroads--Equipment and Supplies
- Subseries Level 3002 - Diesel Locomotives
- ItemWWANT305 - Northern Pacific diesel locomotive number 6506 at Allentown, Washington, circa 1948.
- ItemWWASPSL4-082 - Northern Pacific Diesel Locomotive 7014A, Washington State, undated