(UNDATED) Organizers of the Woodstock Music and Art Fair planned for a crowd of 50,000 at their August gathering 40 years ago in rural New York. Instead, nearly 500,000 people showed up to hear Jimi Hendrix, Janis Joplin and the Who, transforming the festival into an iconic — and some say spiritual — event that still resonates in America.

“A community grew out of Woodstock,” says organizer Michael Lang in his new book, “The Road to Woodstock.” “A sense of possibility and hope was born and spread around the globe.”

Rock historian Pete Fornatale goes further. “I wanted to make the case that Woodstock was a spiritual experience,” says the author of “Back to the Garden: The Story of Woodstock.”

Fornatale is no religious zealot. “I’m not a believer. I’m not a nonbeliever. I’m a wanna-believer,” he says. But he’s clearly on a crusade to explore the spiritual dimensions of the festival, which organizers moved from the town of Woodstock to a farm near Bethel, which means “House of God” in Hebrew.

“Spirituality may not be the first thing people associate with Woodstock,” says Fornatale, who recently talked about his book at the Museum at Bethel Woods, located on the site of the festival. “But young people were searching for an identity and for a meaning that they found there that weekend.”

Fornatale sees the festival as a massive communion ceremony featuring drugs as sacramental substances, hymns like “Amazing Grace” and “Swing Low, Sweet Chariot” performed by Arlo Guthrie and Joan Baez, sermons by musical prophets like Sylvester Stewart of Sly and the Family Stone, and a modern-day re-enactment of Jesus’ miracle of the loaves and fishes exhibited in the communal ethos of festival-goers who shared food with “brothers and sisters” who were hungry.

Not all historians share Fornatale’s reading of Woodstock, but most agree that the Woodstock generation transformed American religious and spiritual life.

“The counterculture became the culture,” says Mark Oppenheimer, who examined changes among Protestant, Catholic and Jewish believers in “Knocking on Heaven’s Door: American Religion in the Age of Counterculture.”

Oppenheimer says the era’s main religious changes were “aesthetic, not theological.” As he explains, “Woodstock, wasn’t about a lot of intellectual content, or sophisticated arguments. Instead, there was an extraordinary artistic, musical, social happening. And that’s what the era was for religion.”

During the 1960s, Southern Baptist seminary students had to fight for their right to wear long hair or sandals. By the ’70s, Oppenheimer says religious leaders realized there was “no virtue in being buttoned-down and square.”

Now, the unbuttoned look is the norm for megachurch pastors like Rick Warren. “No one questions that a burly fellow who stands up front with a beard and a Hawaiian shirt can speak prophetically about the Gospel message,” said Oppenheimer. “That’s not something that would have happened in the 1950s or 1960s.”

San Francisco writer Don Lattin, who has written three books about ’60s spirituality, said a key to the transformations of that decade can be found at the Esalen Institute, a retreat center in California often seen as the birthplace of the human potential movement.

“There was a pervasive shift from the theological to the therapeutic,” said Lattin, author of “Following Our Bliss: How the Spiritual Ideals of the Sixties Shape Our Lives Today.” “It was all about feeling good rather than being good. It was about stress reduction, not salvation.”

Today, the legacy of Esalen can be found at “seeker-sensitive” churches that market to congregants based on their felt needs and Catholic retreat centers that offer sessions on yoga, meditation and the Enneagram.

Lattin’s forthcoming book, “The Harvard Psychedelic Club,” will focus on Timothy Leary, Ram Dass, Huston Smith and other ’60s figures who popularized psychedelic drugs.

“LSD changed the way millions of Americans see reality,” said Lattin. “So many people had glimpses — often terrifying glimpses — of the mystical connection between self and the rest of the universe. This changed the ways Americans looked at body, mind and spirit and ushered in a lot of what was later called New Age.”

And while members of the Woodstock generation were mostly opposed to the Vietnam War, many embraced the computer technology created by the military- industrial complex, said Stanford University professor Fred Turner, author of “From Counterculture to Cyberculture.”

“The communalists of the 1960s had faith in the ability of individuals to use small-scale technologies of communication to create communities of consciousness,” said Turner, who believes this ethos helped shape today’s Internet.

While these authors don’t neglect the dark side of the ’60s, including the breakdown of the family, they argue we are still following in the footsteps of the Woodstock generation.

“These values have spread out into the culture so much we don’t even see them anymore,” says Lattin.