All,
I regret to inform you of the passing of Dennis McClendon, our friend @Mr_Downtown. I believe he helped with some board business & column consultation in the past and always seemed to show up when a map or train or Chicago expert was needed for a real tough question, both here on the boards but also on the radio and other local media. He and I happened to sit next to each other at a Chidope event some years ago and had a chance to chat and enjoy some food and drinks together. He was as pleasant and interesting as you’d expect.
Mr Downtown was quite active around the web and I learned of his death on Reddit. There are more remembrances in the comments there:
https://www.reddit.com/r/chicago/comments/1enxdk4/rip_to_chicago_historian_cartographer_and/