The longest held political prisoner
in United States history is American Indian Movement leader Leonard Peltier of the Chippewa Nation. In 1977 he was convicted of a crime which he didn't commit. Others accused with him were tried earlier &
found innocent of the murder of 2 FBI agents. When Peltier's time came, the FBI used
everything from a witness who contradicted herself to jury intimidation to slant the trial. He has been incarcerated for half a century, while being denied medical treatment for dental problems & diabetes. Every president since his conviction has refused to offer him a pardon. There's a great
documentary about his case called "Incident at Oglala."