Fifty years ago, tens of thousands of people converged on San Francisco’s Golden Gate Park for the “Human Be-In,” a psychedelic celebration that kicked off a year of revelry that would culminate in the Summer of Love. Moved by countercultural principles, entertained by bands like Jefferson Airplane, and bolstered by a boatload of acid, the event immediately became a legend. But as Jon David Cash writes, the activist movement that ensued may have found its most potent symbol in the creation of People’s Park.

At the Be-In, participants in the counterculture mingled with activists, but left the event once the music stopped and the speeches began. Many of the same people took place in the creation of People’s Park, and similar tensions arose when the uneasy alliance that spawnedWestern world,’” in a coalition with no leaders and no rules, writes Cash. Within a weekend, a park had begun to appear.

The activists cleared the lot, planted shrubs, and began to build play structures and other amenities. They held festivals and went to the park to volunteer and play. Then all hell broke loose: The university began to fight back against the ad-hoc park. On May 15, 1969, they began to construct a fence around the park and attempted to evict some 3,000 supporters with the help of police, highway patrol officers, and sheriffs. Faced with the anger of the park’s supporters, police opened fire. Thirty-two people were hospitalized, one person was blinded, another died, and others needed medical treatment. It would become known as “Bloody Thursday.”

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