In the early 1940s, Giancana was involved in a takeover of Chicago's black American lottery payout system for the Outfit.

Conspiracy theorists consider Giancana, along with Mafia leaders Santo Trafficante Jr. and Carlos Marcello, to be associated with the assassination of John F. Kennedy.

[12] Giancana joined the 42 Gang, a juvenile street crew working for political boss Joseph Esposito.

After Esposito's murder, in which Giancana was allegedly involved, the 42 Gang was transformed into a de facto extension of the Chicago Outfit with leaders such as Frank "the Enforcer" Nitti, Paul "the Waiter" Ricca, and Tony "Joe Batters" Accardo.

[citation needed] In 1939, Giancana was convicted of bootlegging and sentenced to four years in Leavenworth Prison and Terre Haute Federal Correctional Complex.

Giancana's crew was also responsible for the August 4, 1952, murder of African American gambling boss Theodore Roe.

[17] Later, Buffalo crime boss Stefano Magaddino and Giancana were overheard on a wiretap saying the meeting should have occurred in the Chicago area.

Giancana claimed that the Chicago area was "the safest place in the world" for a major underworld meeting because he had several police chiefs on his payroll.

[20] Richard Cain, a corrupt police officer, also made "frequent trips" to and from Mexico as Giancana's courier and financial adviser.

[21] Some journalists claimed that Giancana and his Chicago crime syndicate "played a role" in John F. Kennedy's victory in the 1960 presidential election.

[26][24] It is widely reputed and was partially corroborated by the Church Committee hearings that during the Kennedy administration, the CIA recruited Giancana and other mobsters to assassinate Fidel Castro.

"Sam Gold" was Giancana; "Joe" was Santo Trafficante Jr., the Tampa syndicate boss and one of the most powerful mobsters in prerevolution Cuba.

He offered $150,000 for the "removal" of Castro through this operation, though the documents suggest that neither Roselli, Giancana, nor Trafficante accepted any payment for the job.

After six attempts to introduce the poison into Castro's food, Orta abruptly demanded to be relieved of his role in the mission, giving the job to another, unnamed participant.

According to the documents, Robert F. Kennedy prohibited the prosecution of the agent and Maheu, who was soon linked to the wire attempt, at the CIA's request.

[38] Meanwhile, Giancana was deposed as operational boss by Ricca and Accardo, and replaced by Joseph "Joey Doves" Aiuppa.

[42] One of the most violent criminals in U.S. history, Giancana acquired the nickname "Momo," from the slang term "mooner," meaning "madman.

[3] On 23 September 1933[2], Giancana married Angeline DeTolve, the daughter of immigrants from the Italian region of Basilicata, while living in The Island, Chicago.

[49][50] After Giancana's return to the United States, police detailed officers to guard his house in Oak Park, Illinois, but on the night of June 19, 1975, shortly before he was scheduled to appear before the Church Committee,[51] which was investigating CIA and Cosa Nostra collusion,[52] a gunman entered the home through the basement and shot Giancana in the head and neck seven times with a .22 caliber pistol.

At around 11 p.m., Joseph DiPersio, Giancana's caretaker, found his body on the floor of the basement kitchen where he was said to be frying sausage and peppers.

[53] Within days of Giancana's murder, Michael J. Corbitt, the police chief of Willow Springs, Illinois, and a mobster associate, was told by Chicago Outfit's capo Salvatore Bastone that "Sam sure loved that little guy in Oak Park... Tony Spilotro.

[58] Another theory is that Santo Trafficante Jr. ordered Giancana's murder due to fears he would testify about the Mafia's involvement in CIA plots to kill Castro.

Although Trafficante would have needed permission from Outfit bosses Accardo and Joseph Aiuppa, Giancana's murder coincided with the discovery of the decomposing remains of Johnny Roselli in an oil drum floating off Miami; he had been shot and chopped up before being dumped in the sea.