Jack Ruby was an unknown nightclub owner who became instantly famous in November 1963 as the man who shot and killed Lee Harvey Oswald two days after Oswald was arrested for assassinating President John F. Kennedy in Dallas, Texas. The apparent ease with which Ruby entered the Dallas police department garage and then shot Oswald helped fuel speculation about a conspiracy to kill Kennedy. In this scenario, Ruby was allowed to silence Oswald to prevent him from disclosing any incriminating information. Though no proof has ever been produced, Ruby's ties to organized crime gave conspiracy theorists a basis for their claims.

Born Jack Rubenstein on March 25, 1911 in Chicago, Illinois, Ruby dropped out of elementary school and led an unremarkable life. In his twenties he moved to California, where he worked as a singing waiter, a newspaper salesman and other odd jobs in Los Angeles and San Francisco. He returned...