From Wikipedia

Crime Inc.
Episode Four

Birthright of Gangsters

In the mid-20th century the Mafia was reputed to have infiltrated many labor unions in the United States, notably the Teamsters, whose president Jimmy Hoffa disappeared and is widely believed to have been murdered by close personal friend Frank Sheeran, as stated in his book I Heard You Paint Houses. In the 1980s, the U.S. government made a determined effort to remove Mafia influence from labor unions.