What does it take to throw a party for ten thousand of your closest friends? A party that brings famous music acts from all over the country to your stage? A party with unlimited beer. And more than that, a party that brings in serious cash for a good cause.

With enough planning, funding, and support from your community, you might pull it off. But to throw a party like that eight times in a row, you need more. You need the right historical moment.

From 1972-1979, students at the University of Montana at Missoula threw the biggest kegger the Treasure State had ever seen. Known colloquially as the Aber Day Kegger, it was an outdoor concert bash fueled by up to a thousand beer kegs…and an unofficial substance or two. It drew in young music fans from all over Montana, the Pacific Northwest, and as far away as Los Angeles. The kegger helped more than one music group on their way to stardom. And most importantly, the organizers raised tens of thousands for the university library and local causes.

They also irritated a large swathe of Missoulians who looked at the kegger and saw only youthful impropriety, drunk driving, and a stain on a good university's reputation. Ultimately, the party couldn't last forever.

But the rise and fall of the Aber Day Kegger was decided in more places than Missoula's proverbial town square. Its fate was the product of a surging youth drinking culture, shifting minimum drinking age laws, predatory beer marketing practices, some old-fashioned greed, and–for a moment there–a national boycott movement. Shifts in these winds made the kegger possible, and they unmade it just as readily.