The Chicago Express building facade was previously used as Gotham City Police Headquarters in Batman (1966).
In one scene, when Charles and Mr. Edwards are near the trench, if you look at the background behind them, you can see the front and side of the building/set that would later be used as the exterior of the Daily Planet in Lois & Clark: The New Adventures of Superman (1993).
Actor Radames Pera played Mr. Edwards' adopted son, John Sanderson Edwards, earlier in the series, and although he did not appear in this episode, a pencil drawing in his likeness was seen on the mantle in John's Chicago apartment.
John Jr., had been Mary's fiance and yet no one mentioned contacting Mary to let her know what happened to him.