In the 1860s, a man named Charles Guiteau came to Chicago to work as a shystering lawyer. Previously, he had been living with a free love community in New York; their philosophy had been that every man was married to every woman and that everyone should love everyone else. After meeting Guiteau (who the nicknamed Charles Get Out), they changed their philosophy to "everyone should love everyone else except for Charles Guiteau."
By the 1870s, Guiteau, having annoyed the legal profession sufficiently, was living on Dearborn street, right next to what is now the Excalibur club, and working as a preacher. He claimed to have discovered that Jesus had returned to Earth in A.D. 70 (an idea he stole wholesale from the free love sect), and preached in a handful of downtown churches.
When THAT didn't work out, he drifted into politics, and, having made a couple of speeches supporting James Garfield for President, decided that Garfield should make him Consul to Paris. When the Garfield people laughed him out of the White House, Guiteau decided that his best course of action was to shoot Garfield in the chest. And so he did.
His trial was bizarre enough to become the social event of the season. Guiteau would pass notes to random spectators asking for advice, gave his testimony in the form of epic poems (having decided to become a poet), and claimed that HE didn't kill Garfield - the doctors did. This was probably true (Garfield ended up getting poked in the liver a few times while doctors tried to find the bullet. Alexander Graham Bell invented a metal detector to find it, but it didn't work; by the time any of the resident geniuses realized that the metal bed was probably screwing it up, it was too late). But it didn't get Guiteau off the hook - he was sentenced to hang. On the scaffold, he sang a song even worse than the one Carl Wanderer sang on the scaffold in Chicago a few decades later - one of his own composition called "I'm a Going to the Lordy."
We've pinpointed the locations of three building around downtown Chicago where Guiteau lived - one was near Haymarket Square, another was where the Dearborn St. post office is today, and one is next to the Excalibur club. As far as I know so far, none are still standing, but I'm not sure of this yet.
John Wilkes Booth also lived in Chicago briefly (see previous post). Leon Czolgosz, McKinley's assassin, visited Chicago briefly to meet with anarchist Emma Goldman at her home in 1901.