1971 May Day protests against the Vietnam War
The 1971 May Day protests against the Vietnam War were a series of large-scale civil disobedience actions in Washington, D.C., protesting the United States' continuing involvement in the Vietnam War. The protests began on Monday morning, May 3 and ended on May 5.
Source: Wikipedia — 1971 May Day protests against the Vietnam War (CC BY-SA 4.0)