I was there about 6 years or so ago. It really, truly, is on Superior Ave. Strange coincidence, huh? Of course, it's the only thing on Superior Ave. It was a big plant for a small town in it's day.
When I was there, the property was vacant. There were "for lease" signs on the property, and the buildings appeared to be kept up and the grass was cut. The property itself was fenced, the building doors locked, but the flag pole with a plaque dedicating the plant for Superior was accessible on the traffic circle in front of the main building.