Automakers’ archives departments are filled with thousands of photos that will likely never see the light of day. Images of assembly lines are among some of the most obscure documents because they can’t easily be used in magazine advertisements and the auto media rarely has a need for them. Most often than not they were taken purely for the sake of reference.

However, factory pictures have a particularly strong historical value as they reveal what the factory looked like from the inside, how the actual assembly line was set up, the human-to-robots ratio and so forth.

For your enjoyment, we’ve compiled a collection of period photos taken in manufacturing plants.