Different doors for different vehicles, I would guess. White Pine Mine used tire-based vehicles, rather than track-based, making it pretty different than other mines I’ve been to.
Much of the plant depended on steam, not only for heat but for mechanical power.
Part of the grain drier system in ADM #1 crawls up the side of the building like a steel vine.
Quincy Smelter, 2014.
Days after the long-flooded basement was pumped out. Note the water lines!
As the Barker steamed past the dock and island, the sunset casts the shadow of the Taconite Harbor receiving trestle on the boat. Through the fog, you can see some of the islands that were joined into a breakwater.
A natural reaction with this kind of view.
The the left, the nitrating line in War City. To the right, War City’s sole suburb, Charlestown, IN.