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.
Near the guard post protecting the launch pad at the Duluth BOMARC is an orange windsock.
An impressive message for graffiti in a Detroit warehouse, but then again look at these steam pumps. Over-built and under-appreciated.
A long exposure of the launch pad and its dedicated guard shack. In the middle of the base is a tall antenna which was part of the MARS program during the Gulf War. The MARS program helped connect calls between deployed soldiers and their families.
This bridge over Eagle River is beautiful.
A little ice and snow made work at Taconite Harbor much more dangerous.
Looking at The Windy City from the top of the coal tower. The pond you see is the former ACME Coke coal yard.
This heavy door opens directly into the missile vault and was used to load and unload the missile erector.