Railroad Archives Online
- CollectionD0153 - Doug Wingfield Collection
- Series004 - Northern Pacific Railroad Company
- Subseries Level 1014 - Photographs
- Subseries Level 2003 - Railroads--Buildings and Structures
- Subseries Level 3003 - Maintenance Facilities
- ItemWingfield.216 - Northern Pacific Roundhouse at Duluth, Minnesota, 1961