According to the following listing from the July 22, 1948, edition of the Chicago Tribune, Jimmy Stewart appeared on this station from 10:30-10:45 a.m. on that day.
The show is not available, so it is impossible to determine the nature of his visit. However, as mentioned in Jimmy Stewart on the Air, the film Call Northside 777, which took place in Chicago, had been released just a few months previous to this date and that may have been the topic of conversation during his appearance.