The first California Jam festival takes place at the Ontario Motor Speedway in Ontario, California. Co-headlined by Deep Purple and Emerson, Lake & Palmer. The festival set what were then records for the loudest amplification system ever installed, the highest paid attendance, and highest gross in history.

California Jam was a rock music festival co-headlined by Deep Purple and Emerson, Lake & Palmer, held at the Ontario Motor Speedway in Ontario, California, on April 6, 1974. It was produced by ABC Entertainment, Sandy Feldman and Leonard Stogel. Pacific Presentations, a Los Angeles–based concert company headed by Sepp Donahower and Gary Perkins, coordinated the event, booked all the musical talent and ran the advertising campaign. Don Branker worked for Leonard Stogel and was responsible for concert site facilitation, toilets, fencing and medical. The California Jam attracted 250,000 paying music fans. The festival set what were then records for the loudest amplification system ever installed, the highest paid attendance, and highest gross in history. It was one of the last of the original wave of rock festivals, as well as one of the most well-executed and financially successful, and presaged the era of media consolidation and the corporatization of the rock music industry.

Ontario Motor Speedway was a motorsport venue located in Ontario, California. It was the first and only automobile racing facility built to accommodate major races sanctioned by all of the four dominant racing sanctioning bodies: USAC for open-wheel oval car races; NASCAR for a 500-mile (800 km) oval stock car races; NHRA for drag races; and FIA for Formula One road course races. Additionally, several motorcycle races were held at the track. Constructed in less than two years, the track opened in August 1970 and was considered state of the art at the time.

Ontario is a city in southwestern San Bernardino County, California, United States, 35 miles (56 km) east of downtown Los Angeles and 23 miles (37 km) west of downtown San Bernardino, the county seat. Located in the western part of the Inland Empire metropolitan area, it lies just east of Los Angeles County and is part of the Greater Los Angeles Area. As of the 2020 census, the city had a population of 175,265.