I know he's technically not a serial killer, but my favorite fact as a Chicagoan especially is that Al Capone is the reason we have expiration dates printed on perishable food!! His goddaughter or niece once ate moldy bread or something (forgive me I'm going off memory and after an 11 hour shift) and became violently ill and was allergic to penicillin and nearly died, so Big Al got so mad he wrote into the state about it (I wanna say there was a lawsuit as well) and thus, expiration dates on milk, eggs, bread, etc.