I had a friend point out an old structure at 3575 S Highland Drive in Salt Lake, it was recently demolished but can be barely seen in these google streetview screenshots:

It is across the street from the monument for Gardner’s Saw Mill and not too far from where I believe the mill was so I wonder if it’s related to that.

I’m posting this partly to document what the area looked like in 2020 prior to the homes of Millstone Chase being built and partly because I hope someone knows what that structure was – it looks like an old church or school. The pile of rubble of carved stones was still there when I stopped by.