Sure does bring back memories - I saw the below concert at the Philadelphia Spectrum which held about 17,000 but only around 2,000 people showed up (basically the floor of the hockey/basketball arena contained the stage and fold out seats and only a few of the bottom rows of the arena were filled) since many had not heard of some of the bands at this point in time. Others had just began to get known. I still can't believe I saw all the below in one night with such a great vantage point.
"July 12, 1969: Led Zeppelin/Johnny Winter/Al Kooper/Jethro Tull/Buddy Guy’s Blues Band
Many of the acts who played the Spectrum Pop Festival had previously headlined at the Electric Factory. The Summer of 1969 was the Summer of Rock Festivals, however, and bands had started crisscrossing the country"