On the side of a building in Charleston I spied this small door and had instant recognition. A coal chute.
In NYC where I grew up all the tenements had these. The ‘super’ kept the boilers running with coal. A big truck would pull up in the street, a chute placed across the sidewalk, and coal poured into the basements.
I have given this not a single thought in (many) decades. But here it was on a side street in Charleston SC.