For the hundreds of thousands of people who descended on Bethel, N.Y., over a rainy weekend in August 1969, the Woodstock Music and Art Fair was a defining cultural moment — a peaceful demonstration of the glories of rock music, with a starry lineup including Jimi Hendrix, the Who, Santana, the Grateful Dead and a new band called Crosby, Stills and Nash.

But in business terms, Woodstock was a disaster.

In almost all the ways that concert promoters measure the success and smooth operation of their events, Woodstock was a failure. Crowd control was impossible, as fans arrived in droves — estimates went as high as 450,000 — whether they had tickets or not. Sanitation was minimal. Bumper-to-bumper jams snarled roads for miles. (“Traffic Uptight at Hippiefest,” The Daily News declared on its front page.) And the festival’s producers said they ended up $1.3 million in debt — the equivalent of about $9 million today.

Those drawbacks wound up feeding the mythology of Woodstock as a temporary utopia that defied the norms of a materialist society; traffic jams and mud, after all, may have been a small price to pay for uniting a generation through the communal powers of “peace and music.”

Yet the problems of Woodstock — and of Altamont, in California four months later, where a man was killed by a Hells Angels security squad — stunted the growth of American rock festivals for decades. What young fans saw as groovy gatherings, with clothing optional, were viewed by local governments around the country as dangerous and disruptive events that they did not want in their backyards, and they passed laws accordingly.