Born Giacomo Colosimo to Luigi Colosimo and his second wife Giuseppina Mascaro in the town of Colosimi, Province of Cosenza, Italy, he emigrated to Chicago in 1895. Beginning as a small time hood, Colosimo was noticed by First Ward aldermen Michael "Hinky Dink" Kenna and John Coughlin. He worked for them first as a precinct captain and later as their bagman. This provided Colosimo with the political connections that aided him in his rise to power as a mob boss.