Summer Jam 1973
 

I think it's generally believed that Woodstock was the largest rock concert in history. This is a pretty good read on a concert that was twice as big:

http://www.superseventies.com/watkinsglen.html

http://www.glenphotos.com/summerjam/

I remember that, sort of. In the summer of '73, I was a high-school student in Niagara Falls, working my first summer job at a plumbing supply warehouse. I wanted to go to that concert, but so did a co-worker, who was a college student and had been with the company for two years. The boss said only one of us could go, and since my co-worker "outranked" me, he got to go to the concert.

When he returned, he was rather tired. Fortunately, he and I were in the midst of building a series of outdoor bins for plumbing supplies, so nobody bothered us all day long as we talked quietly and worked at a nice easy pace for a couple of days until he got his energy back. At the Watkins Glen concert, he spent all of his meager funds on windowpane and weed and food, and he came back happy and broke. When he told me about his experience, he always had a gentle dreamy smile, and paused a lot and sighed. It was a splendid experience for him.

Thanks for posting that link. :)