One of 2000 tickets that was unused from this 9000 seat outdoor theater. Twenty miles from Denver, its "out of the way" location was blamed in the press for the lack of a sell out, and that was what a lot of people have long believed. However, recent research by Denver resident Scot Raile shows that perhaps not only was the concert sold out, but by more than 1000 seats. Here's his story:
"Evidence that I've seen shows that Red Rocks was full to the brim."
At least one local paper (the Rocky Mountain News) has printed a photograph of the crowd; no empty seats can be seen. I've also seen a brief clip of local news coverage of the show; that, too, shows what appears to be an over-capacity crowd.
So why the 2,000 unsold tickets? It turns out that my high school sociology teacher happened to have attended that show. When I told him that it was sold out, he first looked at me in disbelief, then laughed out loud. "Well, officially it may not have been sold out, but I've never seen Red Rocks more full," he said. So why the discrepancy? He then proceeded to tell me that in 1964, Red Rocks was viewed far more as a National Park than a musical amphitheatre, and, even then, mostly classical music was performed there. As such, there were hardly any gates, ticket takers, bouncers, etc. the way there are today.
Because of this, it was well-known in Denver that there were tons of ways to get into Red Rocks Amphitheater, and having a ticket was only one of them. So he theorized that there were well over 10,000 people there (above and beyond the 9,000 capacity), but only 7,000 actually shelled out for the tickets.