They came to San Francisco seeking something more — something significant, something transcendent. By the summer of 1967, a half-century ago this year, nearly 100,000 hippies and counterculture kids had gathered in the Haight-Ashbury neighborhood to drop acid, indulge in free love, and escape the confining strictures of their middle-class upbringings. They wanted to join the revolution.

Yet the utopia called the Summer of Love wouldn’t last, and, after the movement faded out, not all of them went back to professional career paths. Disillusioned by bad trips and a sense that their pursuit of hedonism had been empty, thousands of burned out hippies soon experienced something possibly even more revolutionary than tuning out and turning on: a born-again religious conversion.

Sex, drugs, and — Jesus? It’s not what the Summer of Love generally calls to mind. But of all the things that came out of San Francisco in 1967, perhaps none was more unexpected, or more consequential, than the Jesus Freaks or, as they were more commonly known, the Jesus People.

While they would give up their drugs and promiscuous sex, the Jesus People retained much of their countercultural ways, bringing their music, dress, and laid-back style into the churches they joined. Their influence would remake the Sunday worship experience for millions of Americans. As the historian Larry Eskridge has argued, today’s evangelical mega-churches with their rock bands blasting praise music and jeans-wearing pastors “are a direct result of the Jesus People movement.”