John Sinclair, a counterculture icon who managed Detroit rockers MC5 during their peak years, has died. He was 82. His representative confirmed that the Michigan native died of congestive heart failure, The Detroit News reported.

In addition to managing MC5, Sinclair was known as a poet, a political activist, a vocal marijuana advocate and the leader of the White Panther Party, an anti-racist group named in response to the radical Black Panther Party.

"He was on the forefront of the marijuana movement," Sinclair's representative, Matt Lee, told The Detroit News. "But I don't think people realized how knowledgeable he was in American music and he was a certified expert in all forms of American jazz and rhythm and blues."

READ MORE: MC5 Guitarist Wayne Kramer Dead at 75

Sinclair started managing the band in the mid-'60s and was with them when they recorded their classic live album Kick Out the Jams in Detroit in 1968. The album is best known for its rallying cry "Kick out the jams, motherfuckers!," but the record remains a milestone work in rock music, noted for its influence as a proto-punk masterpiece.

MC5 guitarist Wayne Kramer, who spent time in prison for drug possession in the '70s, died in February at the age of 75 of pancreatic cancer.

Why Did John Sinclair Go to Prison?

Sinclair also spent time in prison on drug charges. In 1969, after two previous busts, he was sentenced to 10 years for possession of two joints. In 1971, John Lennon and Yoko Ono were at an Ann Arbor rally with 15,000 people to protest the sentence. Within two days, Sinclair was set free. Lennon later included a song called "John Sinclair" on his 1972 album, Some Time in New York City.

Even though Sinclair and MC5 ended their professional relationship in 1969, the year Kick Out the Jams came out, Kramer still admired his mentor. "He's an incredibly persuasive and charismatic person," the guitarist told Rolling Stone in 1971. "He's this great big cat and he's got all this energy, and he just turns it on you.

"There is something to John's father-figure effect on the group. I had just left home, and here was this older cat who could explain all these things that I didn't understand about the world. And he did have a strong effect on everyone else, philosophically strong spiritual attitudes that he instilled in us."

Iggy Pop, another Detroit music legend who came of age along with MC5 in his band the Stooges, paid tribute to Sinclair on social media following his death. "He was a truly interesting man, one of a kind," he wrote. "Thanks and praises."

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Gallery Credit: Allison Rapp

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