Oleum was an

unincorporated community An unincorporated area is a region that is not governed by a local municipal corporation. Widespread unincorporated communities and areas are a distinguishing feature of the United States and Canada. Most other countries of the world either have ...

in Contra Costa County,

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

, United States, located between the unincorporated town of Rodeo and Tormey. It was a small company town, with housing for

Union Oil Union Oil Company of California, and its holding company Unocal Corporation, together known as Unocal was a major petroleum explorer and marketer in the late 19th century, through the 20th century, and into the early 21st century. It was headqu ...

company workers, hence the name, derived from "petroleum". The refinery still exists. The site is located on the Mexican land grant Rancho El Pinole made to Ygnacio Martinez. A post office operated at Oleum from 1910 to 1951.

References

Unincorporated communities in California Unincorporated communities in Contra Costa County, California {{ContraCostaCountyCA-geo-stub