Besides images of machine parts and motor vehicles, the Glass Plate Series contains thousands of images showing workers in International Harvester factories. Some were taken to illustrate working conditions and carefully staged to convey a message. Others were created mainly to document industrial processes but the staff, who were considered peripheral when the shutter was snapped, have unintentionally evolved into the most interesting elements in the photo. Still others appear to be deliberate portraits of workers, perhaps taken at significant events like anniversaries or retirements.

Taken together, these images are a tremendously rich source of information on working-class Americans at the peak of the industrial age. Because they were captured on large-format glass plates, the subsequent scans are unusually rich and vivid.