In the 1920's Chicago was ruled by chief gangster Al "Scarface" Capone. Around 10:30 am on this day February 14, 1929, the rash of Chicago violence reached it's climax. In a garage in Lincoln Park (2122 N Clark St) on Chicago's north side, six of George "Bugs" Moran's men (one unlucky bystander who happened to be a mechanic) were shot to death by several men dressed as police. Capone was never directly linked to the murders, but he was generally considered to be responsible. The infamous mob hit became known as the St. Valentine's Day Massacre.
P.S. 'The Chicago Worker' mechanic shirt was inspired by these events.