"All the stars were aligned," said Gellman. "It could have been a disaster and wasn't because everyone was so mellow and high."
They left the site during Jimi Hendrix's signature finale of "The Star Spangled Banner," and ended up barefoot and hungry at a rest stop with photos of the event spread across newspaper front covers.
"We knew then we were part of a historical event," he said.
Today, at 57, Gellman conducts research for the National Institutes of Health and teaches one college course -- "PSY 305, Drugs and Behavior."
Barry Levine was only 26 when he took the still photography that was later used in the 1970 documentary, "Woodstock."
He has followed many of the old Woodstock bands on gigs around the country. "There are a lot who are dead, but the folks who are still alive are still kicking," he told ABCNews.com.
"People don't give a sh*t what year it was," said Levine, who just published "Woodstock Storybook" with his wife, Linanne Sackett, whom he met in Bethel.
"Woodstock still represents something," he said. "But there won't be that many of us around for the 50th."
At 18, Kathee Miller traveled to Woodstock with a boyfriend she met on the New York City subway.
"We were foolish and music driven," said the now 56-year-old California psychotherapist. "We didn't bring supplies. We bought an inflatable tent for ten bucks and woke up in the woods one rainy morning to find ourselves floating downhill."
"We laughed back then," she told ABCNews.com. "No problems."
The Hog Farm, a spontaneous cooperative between Wavy Gravy and the local farmers, fed Miller and other hungry hippies.
Today, Miller is on the faculty of Pacifica Graduate Institute in Santa Barbara and still holds on to the love beads she wore around her neck.
"Though we were much more naive, I think the passion of protest and the passion for living out loud and loving art and music and dance carried me to this age in life still dancing," she said.
Janie Hoffman's photo appeared in Life magazine, just to the right of the centerfold. At 17, she bought a weekend pass for $45 from a friend who was busted for a joint found on the floor of his car.
"Did I mention I went to jail to buy the ticket?" Hoffman told ABCNews.com. "The ticket was in his wallet, the wallet was with the desk sergeant and the money was for his bail."
Hoffman, who is 57 and living in Venice, Calif., was the only girl in her group allowed to go. "My father had to convince my mother. He fished up in that neck of the woods all the time and knew it was safe."
Posters were everywhere and tickets were promoted on radio stations. "They kept saying, if you don't have a ticket, don't come."
She and a half million others got stuck in traffic on the New York Thruway, which came to a dead stop for hours. "Everyone was out of their cars, sharing food, drink and more."
By the time they arrived the chain link fence was down and promoters declared it a free concert. The stage was still being built. "The heat, the humidity, combined with well, you know, caused a lot of us to simply lay down and take a nap."
When I woke up, it was dark. Folk singer Arlo Guthrie ("Alice's Restaurant") had asked everyone to strike a match.
"The light went as far as your eyes could see," she said. "Until that point, we had absolutely no idea how many thousands and thousands of us were there."