John Snow Cholera Data

In 1854, Dr. John Snow famously put cholera death data on a map to help readers see that reported deaths in Soho, London were in the vicinity of the Broad Street pump, which was the source of the contagion, as well as to shift from an understanding of cholera as airborne to waterborne. Snow's map certainly reinforces the value of putting data on a map to help readers see the patterns revealed, which is as important to contemporary thematic mapping as it always has been — geography and cartography were showcased during the Covid outbreak.

Such mapping techniques aren't just useful for infectious disease epidemiology, but it should be noted that the maps still need to be reviewed and analyzed, not just created. A sad reminder of this is the recent court appearance of Lawrence Reed, the man charged with setting a woman on fire on a Chicago Transit Authority subway train on Nov. 17. With more than half of her body burned, the victim — who reportedly remains in critical condition — got off the train and collapsed at the Clark/Lake CTA stop, just a few hundred feet away from Chicago's City Hall, which Reed was also later charged with trying to burn down just three days earlier on Nov. 14. In a press conference, Chicago Mayor Brandon Johnson suggested the Nov. 14th City Hall arson may have been political in nature ("this type of violence has no place in our politics"). Days later, he called the Nov.17th CTA fire attack horrific but isolated, but later recharacterized it as an 'absolute failure' of justice, mental health systems after reports broke of Reed's extensive criminal record ("This individual was charged with dozens of felonies over the past three decades," Johnson said. "He was clearly seriously mentally disturbed and was a danger to himself and to others. The system that we had failed to intervene.").

Incredibly, Reed's past felonies also included trying to burn down the State of Illinois' Thompson Center (now being rehabbed by its new owner, Google) — which is across the street from the site of the City Hall arson attack and houses the station where the CTA fire attack victim collapsed — on April 23, 2020 as Governor JB Pritzker was preparing to hold his daily COVID-19 press conference inside the building.

So, while it may be a little unfair to "armchair quarterback" the investigation into Reed's November 2025 arson crimes with the benefit of hindsight, one can't help but wonder: Would a simple review of a Chicago Crime map for historical arson crimes in the immediate vicinity of City Hall (map) right after the Nov. 14th arson have called out Reed's 2020 arson (map) at the State of Illinois Thompson Center and led to his apprehension before he got the chance to set afire the woman who collapsed at the subway station in the Thompson Center (map) three days later, especially since Reed's whereabouts were readily available from the electronic ankle monitor he was wearing while awaiting trial for another violent attack?

By the way, don't count on Copilot to automatically connect the map dots for crimes. An attempt to do so was initially stymied by Copilot's refusal to even acknowledge Reed had any connection to the horrific CTA arson attack.