The 1970s had two major events that had implications for journalism. One was the publication in June 1971 by the New York Times of a top secret history of the US military involvement in Vietnam from 1945-1967, now called the Pentagon Papers, that had been leaked to it by a then-unknown mid-level intelligence analyst named Daniel Ellsberg.
As Wikipedia says:
The papers revealed that the U.S. had deliberately expanded its war with bombing of Cambodia and Laos, coastal raids on North Vietnam, and Marine Corps attacks, none of which had been reported by media in the US. The most damaging revelations in the papers revealed that four administrations, from Truman to Johnson, had misled the public regarding their intentions.