The Ontario Motor Speedway was the home of the first California Jam on April 6, 1974. A co-headlined event the California Jam Festival was spearheaded by Deep Purple and Emerson, Lake & Palmer. The last of the mega concerts held the record for the most paid for tickets for the time. Woodstock had more people but less shelled out real money.
The total list of performers in order of appearance: Rare Earth, Earth, Wind & Fire, Eagles, Seals and Crofts, Black Oak Arkansas, Black Sabbath, Deep Purple and Emerson, Lake & Palmer. Unlike the giant shows before this a formal filming and broadcasting of the event never go finalized. Funny further seeing how ABC was one of the sponsors at the time.
However one of my favorite versions of Burn from Deep Purple was recorded during this show and released on California Jamming LP then CD. Although not perfect is a killer reflection of the David Coverdale version of Deep Purple.