Giacomo Colosimo (born February 16, 1878 – died May 11, 1920) better known as "Big Jim Colosimo", was an Italian-American crime boss who built a criminal empire in Chicago based on prostitution, gambling, and racketeering. He gained power through petty crime and the heading of a chain of brothels. From about 1902 until his death in 1920, he led a gang that would ultimately be known as the Chicago Outfit. Johnny Torrio, an enforcer Colosimo imported in 1909 from New York, seized control after his death. Al Capone, a Torrio henchman, would later lead the infamous Outfit and bring it onto a national scale.
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.
Later on, Colosimo acquired another nickname, "Diamond Jim." This name was given to him because he frequently dressed in a white suit and wore diamond pins, rings, and other jewelry. This jewelry, combined with his charm and money, helped him establish relationships with women. He had a strong interest in women and money, which fueled his enthusiasm for prostitution. In 1902, Colosimo married Victoria Moresco, an established Chicago madame, and the two opened a second brothel. Within a few years, Colosimo expanded his business to nearly 200 brothels and had made inroads into gambling and racketeering.
By 1909, Colosimo was being seriously threatened by the Black Hand gang in Chicago and realized he needed help. He brought John "The Fox" Torrio to Chicago from Brooklyn and made him his second in command. The following year, Colosimo opened a self-named restaurant, Colosimo's Cafe, at 2126 South Wabash, in Chicago. In 1919, Torrio and Colosimo opened a brothel at 2222 South Wabash called Four Deuces. Torrio brought his old Brooklyn lieutenant, Al Capone, to work there as a bartender and bouncer, providing Capone his introduction to Chicago.
When prohibition went into effect in 1920, Torrio pushed for the gang to enter into bootlegging, but Colosimo refused. In May 1920, Colosimo went out of town to marry his second wife, Dale Winter, after he had deserted his first wife. When Colosimo returned to Chicago a week later, Torrio called him and let him know about a shipment arriving at his cafe. When Colosimo appeared at the cafe to wait for its delivery, he was shot and killed. The initial murder suspect was his new wife Dale, but no one was ever arrested for the murder. It was widely believed that Torrio ordered Colosimo's killing so that the gang could enter the lucrative bootlegging business. Torrio reportedly brought in New York colleague, Frankie Yale, to murder Colosimo. Al Capone has also been suspected as Colosimo's assassin.
Colosimo was the first to organize disparate parts of Chicago's crime scene. After his death, his gang was controlled first by John Torrio and then by Al Capone. It became the infamous Chicago Outfit.