On April 15, 1967, as many as 400,000 protesters marched from Central Park to the United Nations to demand an end to U.S. military involvement in Vietnam, with Martin Luther King Jr. leading the way. It was the largest antiwar demonstration in U.S. history to date.

The march was planned by the Spring Mobilization Committee to End the War in Vietnam (“the Mobe”), a loose coalition spearheaded by 82-year-old New York peace activist A.J. Muste. The Mobe reflected alliances between the city’s longtime pacifists and a new generation of radical youth who sought to end the war and change the world.

New York was home to many of the nation’s key antiwar organizations, which attracted a diverse range of antiwar youth, artists, veterans, elected officials, and the middle class. But conflict over the war also increasingly divided the city: in 1970, construction workers attacked antiwar protesters on Wall Street in what became known as the “Hard Hat Riot.”

In 1975, after more than 4,000 New Yorkers had died in Indochina, protesters gathered again in Central Park to commemorate the war’s end, but trauma and divisions from the Vietnam War remained.