The immovable object was the Vietnam war, rounding on its 30th month with no sign of stopping: close to half a million American troops were now waging total war against a frustratingly spectral — but deadly — enemy. The unstoppable force was the counterculture movement, the baby boomer generation that had now reached their teens and were launching wave after wave of protests in resolute opposition to war of any kind. The two met in 1967, producing a series of defining moments in American history.

On this day, October 21, in 1967, an estimated 70,000 (and possible as many as 100,000) protesters descended on the Lincoln Memorial in Washington D.C. in the first of what would become biannual anti-war protests.

A rally at the memorial with speeches by an eclectic crowd, including the well-known pediatrician-turned-author, Dr. Benjamin Spock, was followed by a march to the Pentagon. There, Abbie Hoffman — he of the YIP anti-political party that would be heavily involved in the following year’s clashes at the DNC convention in Chicago — began a group chanting and singing session to try and levitate the institution and drive out all the evil spirits from it.