- For other uses, see Chicago.
- Two different starships named Horizon have been said to have left Chicago Mobs of the Twenties behind on Sigma Iotia II.
ECS Horizon crewman Nora Melchior kept a hardcopy on a shelf in her quarters, when friend Travis Mayweather spoke to her, in private. (ENT episode: "Horizon") When the Horizon visited Sigma Iotia II in 2155, the book was traded to the Iotians by the ship's crew. (ENT novel: Kobayashi Maru)
Chicago Mobs of the Twenties was a reference work used by the USS Horizon first contact team when they visited Sigma Iotia II in 2168. However, they left their copy behind when they broke orbit. (ST reference: The Worlds of the Federation, Decipher RPG module: Worlds)
The Iotians viewed the society depicted in the book as ideal, and rebuilt their own accordingly, quickly adopting "the Book" as it became known as something of a cultural bible. Copies of the book are found everywhere in Iotian society, including the headquarters of every major Boss; culturally, Iotians treat the book with near-religious reverence, and tolerate no disrespect against it. The first Federation starship to see this cultural contamination into effect was the USS Enterprise (TOS episode: "A Piece of the Action"; ENT novel: Kobayashi Maru)