What became the defining event of the “free love” 1960s hippie counterculture began as a small business venture.

Four entrepreneurs talking about starting a recording studio in New York’s Catskill Mountains came up with the idea of staging a massive open-air concert instead.

They called it the Woodstock Music & Arts Fair. They sold 186,000 tickets. Some of the most popular rock musicians in the world were signed up to play, including The Grateful Dead, The Who, Jimi Hendrix and Janis Joplin. Film and recording crews were hired to document the gathering.

Word spread quickly, and thousands more than the 186,000 people who bought tickets started streaming to the remote farmland in upstate New York. With little security and little choice, the organizers cut down the fences meant to keep gate crashers out. Woodstock was now a free concert, open to all. As word spread, as many as 500,000 people made the pilgrimage to what was becoming the biggest rock concert of all time. News crews descended, ready to report on the rioting they believed to be imminent.

Folk singer Richie Havens kicked off the festival on August 15, 1969 with the song “High Flyin’ Bird.” Over thirty bands followed over the next three days before the original guitar hero Jimi Hendrix closed the festival.

Yet despite shoulder-to-shoulder crowds, torrential rains, lack of sanitation, and dwindling food and water, the expected violence never materialized. Two people died — one of an overdose, one in an accident — and two babies were born. Impressed with the hippies’ behavior, the farm’s owner, Max Yasgur, said at the time: “If we join them, we can turn those adversities that are the problems of America today into a hope for a brighter and more peaceful future.”

While Woodstock may not have led to Yasgur’s hoped-for peaceful world, it did put the emerging 1960s counterculture smack in the center of popular youth culture. And while there have been several festivals that used the name “Woodstock” since 1969, this year’s 40th Anniversary “Heroes of Woodstock” concert is special, because several of the bands who played at the original Woodstock will be playing again in the same exact location — on what used to be Max Yasgur’s farm.

“It’s a thrill to have so many original performers returning this August,” said Shannon McSweeney-LeMay, the rep for the Bethel Woods Center for the Arts, which was built on Yasgur’s land and is hosting the show. ”Bethel Woods is the place to celebrate the legacy, to share a piece of history, to reflect on what occurred here 40 years ago, and to hear some of the same music fill these hills again.”

MORE: Click here for more information on the Heroes of Woodstock 40th Anniversary Concert.