John Armstrong is credited with inventing the vertical turnout. On his Canandaigua Southern model railroad, they connect the verge with the hidden ore tracks. It’s a manifestation of the empties in, loads out. The empties just got hauled in by the mine switcher from verge, which is the end of the run ready to be loaded in the mine. The vertical turnout is raised and the little switchers will push the empties back, essentially to Pittsburgh.
Some believe that John also invent hidden staging areas. However, he credits Frank Ellison. Although Ellison didn’t refer to it as staging, he operated in this fashion. However, his staging yards were at both ends of the railroad, which were visible. This was a similar concept to hidden staging areas used by John. Of course if there is room to do this, it certainly is a lot more convenient to have staging above ground.