Woodstock turns 40 this weekend, long after most of its attendees did the same. Yes, that muddy, mind-altered weekend on Max Yasgur’s farm has entered middle age, which makes it, in the parlance of its day, 10 years too old to be trusted.

Chances are you’ve already read, seen and heard a few arguments over what this benchmark means to music, culture, commerce, politics, drugs, sexuality, morality and the price of tea in China. The Woodstock generation sold out. The Woodstock generation lives on. Woodstock was the end of the ’60s. Woodstock was the start of the ’70s. Woodstock was Snoopy’s best friend.

By now it’s safe to say Woodstock means pretty much anything you would like it to mean. Such is the fate of events that morph into symbols against their will.

For those who were there, or wish they were, Woodstock was a peaceful gathering of tribes never to be replicated. For those who wanted to direct the revelers to a barber and a bathtub, Woodstock is still an epithet on par with “New Dealer” and “universal health care.”

So how do we extract Woodstock from its symbolism? Perhaps by looking at its surroundings. These included two sordid stories of ’69. These events also are symbols, though they aren’t celebratory. And they share Woodstock’s hindsight burden of representing a tumultuous decade’s final act.

The weekend before Woodstock, seven mutilated bodies were discovered in two separate posh Los Angeles neighborhoods. Five lay dead at the home of actress Sharon Tate, who was pregnant. The words “Death to Pigs” were scrawled in the victims’ blood. Months later the world would learn of Charles Manson and his “family,” zonked-out runaways and drifters persuaded by their cult leader to kill the rich. The same press that would celebrate Woodstock as a communal Utopia had a field day with stories of crazed hippies on the warpath, the nation’s drug-addled youth on a fast track to hell.

Four months later, at the Altamont Speedway in Northern California, came the anti-Woodstock. Of course that’s not how promoters planned the Dec. 6 free concert. They saw it as Woodstock West, a chance to showcase the Rolling Stones, those rock ’n’ roll bad boys who didn’t perform at Woodstock.

A last-minute venue change meant a dearth of first-aid tents and toilets. Worse, someone had the bright idea of bringing in the Hell’s Angels for security — and paying the hell-raisers with beer. Four people died that day, including Meredith Hunter, an armed 18-year-old stabbed multiple times by an Angel of death.

As seen in the subsequent documentary, Gimme Shelter, violence and chaos were the order of the day, with a generous side order of acid and amphetamines. In hindsight the Altamont fiasco and the Manson rampage were widely seen as the “end of the ’60s.”

Again, the power of symbols comes into play. Altamont was no more a post-peace-and-love apocalypse than Woodstock was the high-water mark for the decade’s ideals. After all, the ’60s brought seismic shifts in civil rights, women’s rights and youth culture. The ’60s saw political assassinations, burning cities and the escalation of a war that wouldn’t end. In short, a lot happened — far too much to pin otherworldly significance on a couple of rock concerts.

Was Woodstock impressive and important? Of course it was. A visit via the epic director’s cut of the 1970 documentary makes for a vivid reminder. (The Altamont doc Gimme Shelter was also a 1970 release.) Most of the artists brought their A-game, from the Who’s Pete Townshend showing off some NBA-worthy hops to Jimi Hendrix turning “The Star-Spangled Banner” into a statement of controlled fury.

Also noteworthy: the lack of shoving and jostling in a crowd that pushed into the hundreds of thousands. Talk about peace and love. Frequent concertgoers will testify that you can’t assemble 2,000 indie rock fans today without a few idiots making their presence felt. Bad vibes, man. Anyone who wants to call out the Woodstock kids had best take the step of acknowledging their mature behavior.

So why can’t we just let it be? Why must we do the anniversary rehash dance of books, magazines, TV specials and the like?

The answer may be obvious, but it also makes an ironic addendum to what became a free concert. The baby boomers made Woodstock. Now they market it at every turn. The show at the farm lives on as a cash cow, one more commodity in the marketplace of nostalgia.

So go ahead, let Woodstock symbolize what you please. Memories mean money. And remember, the 41st anniversary is right around the corner.

Movie critic Chris Vognar was born the year after Woodstock. He has just returned from Harvard University, where he was on a Nieman Fellowship focusing on issues of race and ethnicity in America.