On June 13, 1971, the New York Times ran the first of a nine-part series of excerpts from a classified study of U.S. military involvement in Vietnam completed by the Department of Defense. The papers were turned over to the Times by military analyst Daniel Ellsberg, who had surreptitiously photocopied them starting as early as 1969. U.S. Senator Mike Gravel, a Democrat, also entered 4,100 pages of the study which came to be known as the Pentagon Papers to the Senate record, thus making their later publication in book form constitutionally sound.
So what was in the Pentagon Papers? Oh, you know, just proof that the U.S. secretly bombed Cambodia and conducted coastal raids on North Vietnam, and that four Administrations from Truman's to Johnson's had deliberately lied to the public. Ellsberg was put on trial for theft and conspiracy under the Espionage Act of 1917, but a series of legal missteps and dubious evidence-gathering tactics led the judge to dismiss all charges.