In May 1973, amid a flurry of revelations about the Nixon administration that became the Watergate scandal, charges against Mr Ellsberg were thrown out.
Mr Ellsberg, who obtained the documents while working for the Rand Corporation, was disgusted by the government lies he was confronted with.
The whistleblower whose actions in leaking the Pentagon Papers 50 years ago inspired the movie The Post and who faced life in prison for doing so, has claimed Donald Trump is in some ways more sinister and dangerous than Richard Nixon.
In the film, Mr Ellsberg is played by Matthew Rhys, who spent a day with the octogenarian to prepare for the role.