Eliot Ness became famous as the federal agent who led an incorruptible group of law enforcement officers dubbed "The Untouchables," the ones who brought down Chicago gangster Al Capone in the 1930s. Ness didn't really nab Capone -- the mobster was jailed on tax violations, not on any evidence Ness had -- but Ness and his agents routinely disrupted Capone's illegal alcohol industry from 1929 until 1932. Young, brash and courageous, Ness emerged as a heroic crime-fighting figure from his battles with Capone, but by 1935 he had resigned as a federal agent. He became Safety Director for the city of Cleveland, Ohio, where he fought corruption and vice for seven years. He resigned abruptly in 1942 after his involvement in an early morning auto collision -- he had been drinking, hit another car and then left the scene of the accident. Ness served on the board of directors for the Diebold Corporation (the safe and vault company) for a few years, had a few business failures and died of a heart attack just before the publication of The Untouchables (1957), his retelling of the story of his battles against gangsters. The book inspired a popular ABC television series (1959-63), a movie (1987, with Kevin Costner) and a syndicated TV series (1993).
Eliot Ness was a federal agent but never an F.B.I. agent, although he did work for J. Edgar Hoover for just over a month, just as Prohibition was ending.