Herman Wallace was freed on Tuesday after Judge Brian Jackson ruled his 1974 trial had been “unconstitutional” and ordered his immediate release.
He was suffering from terminal liver cancer and died with supporters by his side early this morning. He was 71.
Mr Wallace had been part of the Angola Three, who were originally imprisoned for robbery at the notorious Louisiana State Penitentiary, known as Angola because of its historic links to the African slave trade.
The men say they were framed for the killing of a guard because of their membership of the militant Black Panther party and fight for the civil rights of prisoners.
Robert King, 70, a fellow member of the Angola Three released in 2001, told the Independent: “My reaction is one of sadness for a life wasted. And when I say, wasted, I mean the society he lived in may have considered him a waste, but he helped rewrite history.
“When his conviction was overturned it cleared the slate – he could die a man not convicted of a crime he was innocent of.”
Tessa Murphy, a campaigner for Amnesty International, said: “The Louisiana prison authorities put this man through hell.
“There were longstanding concerns about the safety of his conviction and it’s some small consolation that Herman died a free man.”
Albert Woodfox, 66, is still in solitary confinement and undergoes daily cavity searches.
Mr King added: “When we started out we weren’t thinking about ourselves, we were dealing with the system. That goes on.”