| Ontario Motor Speedway|
| Opened: September, 1970|
| Closed: November, 1980|
Ontario Motor Speedway (nicknamed "The Big O") in Ontario, California, was a 2.5 mile track built similar to the Indianapolis Motor Speedway in Speedway, Indiana. The track was built for $25.5 million and was considered state of the art at the time. Track Management planned to make OMS as a replica of Indianapolis with only a few exceptions. The racing surface was one lane wider and the shortchutes were banked unlike Indianapolis, which made OMS slightly faster. In addition, OMS was built with an infield road course, making it a multi-purpose facility. At the time, Indianapolis did not have an infield road course, and one was not built there until 2000. OMS also included a special gift from Indy. A circle of bricks unearthed from the Indianapolis Motor Speedway were laid in OMS's victory lane.
The first race, The California 500, (held on September 6, 1970), was a success. The Indianapolis 500 was traditionally held Memorial Day weekend, so track officials figured Labor Day weekend was a perfect choice for this new event, However, it never lived up to the success of the inaugural event, and the track started a downhill slide soon afterward. Lack of promotion and an inability to capitalize on the inaugural race's success contributed. It was planned to be part of the Indycar series triple crown along with the Indianapolis 500, and Pocono 500, however, only the Indy 500 remained a household name. OMS held the California Jam concert in order to promote the track more. The California Jam featured numerous rock music bands, and was profitable for the track. NASCAR was running at OMS for a few years and would hold the last race of the NASCAR Winston (now Nextel) Cup Series there until the 1980 racing season. The facility also featured a dragstrip which hosted NHRA events.
Track management went bankrupt and the speedway was deemed a financial failure. 1980 would be its last year of operation and the City of Ontario sold the track for $10 million to Chevron Land Management. The track was demolished in 1981 at a cost of $3 million and left as an empty lot. The property remained vacant for several years until the mid-1980s when a Hilton Hotel was built on turn 4 of the old speedway site. It was the first multiple story building of its kind in the City of Ontario.
As of the mid 2000s, development on the property has increased. Over half of the old speedway property, adjacent to Interstate 10, has been developed commercially.
After the failure of the California 500, the Indycar series replaced the race with the Michigan 500 at Michigan International Speedway. Eight years later in 1988, Riverside International Raceway in nearby Riverside, California also was sold and demolished, in favor of development. With the exception of the Long Beach Grand Prix, all motorsports in southern California was gone until California Speedway in Fontana, California opened in 1997, just five miles from the former site of OMS.
- 1973-Benny Parsons, while running for the Winston Cup championship suffers an early accident. Parsons pulls into the pits and rival pit crews gather parts from the garage and put the damaged car together again. Parsons drives to his first Winston Cup championship. It also should be mentioned, Parsons won the final race at Ontario Motor Speedway.
California 500 Winners (1970-1980)
All winning drivers were American.
| Season|| Date|| Winning Driver|| Chassis|| Engine|
|1970||September 6||Jim McElreath||Coyote||Ford|
|1971||September 5||Joe Leonard||Colt||Ford|
|1972||September 3||Roger McCluskey||McLaren||Offy|
|1973||September 2||Wally Dallenbach Sr.||Eagle||Offy|
|1974||March 10||Bobby Unser||Eagle||Offy|
|1975||September 9||A.J. Foyt||Coyote||Foyt|
|1976||September 5||Bobby Unser||Eagle||Offy|
|1977||September 4||Al Unser||Parnelli||Cosworth|
|1978||September 3||Al Unser||Chaparral||Cosworth|
|1979||September 2||Bobby Unser||Penske||Cosworth|
|1980||August 31||Bobby Unser||Penske||Cosworth|