In my first year or so of tours, I was mostly repeating the stories I heard from other guides and "ghosts of Chicago" books. A major task of mine since then has been to filter out all the misinformation. Some of the stories were completely made up. Others were just a little bit off - like the story I heard about John Wayne Gacy when I was first studying up....
With serial killer John Wayne Gacy back in the news as a handful of his previously unidentified victims being exhumed for possible ID, ghost tours in the city are naturally bringing him up.
A common story is that he met up with many of his victims (the number 27 out of 33 gets bandied about) in a Trailways Bus Station, then brought them into the alley known as "Death Alley" behind the former Iroquois Theatre - a common stop for just about every ghost tour in town.
The story is a little bit off. Gacy met one victim, his first known one, at the Greyhound station that used to stand at Randolph and Clark. It would be the next alley over on the other side of Dearborn from the "Alley of Death and Mutilation." That station has been gone since the early 1990s; the Chicago Title and Trust building was built in its place. So the alley in question would have been in site of the alley Gacy could have used, but it wasn't the same one.