40 years later, Jimmy Hoffa mystery endures

It's been 40 years since Jimmy Hoffa mysteriously disappeared, and the fascination surrounding the whereabouts of the infamous labor leader continues today.

James Riddle "Jimmy" Hoffa was president of the powerful U.S. Teamsters union from 1957 to 1971. He was widely known to have been involved with organized crime.

Hoffa eluded being convicted for years but in the early 1960s, Hoffa was a prime target for Bobby Kennedy, who was appointed U.S. Attorney General by President John Kennedy in 1961. Kennedy aggressively went after organized crime and targeted Hoffa for labor racketeering.

In 1964, Hoffa was convicted of jury tampering and sentenced to eight years in prison. He was also later found guilty on fraud and conspiracy charges, receiving another five years. In March of 1967, he was sent to Lewisburg Federal Prison in Pennsylvania and began his 13-year sentence.

Hoffa, who never resigned from the Teamsters while in prison, was released after 58 months when President Richard Nixon commuted his sentence in Dec. 1971 with the stipulation that Hoffa stay out of union politics until 1980.

On July 30, 1975, Hoffa vanished from the Detroit-area Macchus Red Fox restaurant -- where he reportedly went to meet Anthony Provenzano and Tony Giacalone to settle a feud -- without a trace. His disappearance spawned an obsession lasting decades, though, many believe he was most likely murdered by former Mafia associates.

Theories abound and have become part of American folklore. In the 80s, Hoffa was thought to be buried in the end zone of Giants Stadium. According to one snitch, Hoffa's body was part of the foundation of a public works garage in Cadillac, Michigan. Another claim was that he was buried under the helipad of the Sheraton Savannah Resort Hotel, owned by the Teamsters at the time. ("Saturday Night Live" speculated that he was inside R2-D2 from Star Wars fame).

Hoffa's disappearance has been the subject of countless books, movies and speculation.

The mystery continues. Riddle indeed.