TIL Martin Luther King Jr. said he experienced far more hatred in Chicago than he ever did in Alabama or Mississippi. King took part of the Chicago Housing Movement in August 1966 with thousands of local whites jeering, throwing bricks, and displaying Confederate and Nazi signs all over the city.
TIL in WWII, weather reports were censored to prevent enemy submarines from learning about conditions. A football game in Chicago was so covered in fog that the radio announcer couldn't see the field, but afterwards he was officially thanked for never using the word "fog" or mentioning the weather.
TIL that the St. Patrick's Day tradition of dyeing the Chicago river green arose by accident when a group of plumbers used green dye to trace illegal substances that were polluting the river. The dyeing of the river is still sponsored by the local plumbers union.