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 headquartered in El Segundo, California, United States.

El Segundo is a city in Los Angeles County, California, United States. Located on Santa Monica Bay, it was incorporated on January 18, 1917, and is part of the South Bay Cities Council of Governments. The population was 16,731 as of the 2020 census, a 0.5% increase from 16,654 in the 2010 census. A significant center of the oil and aerospace industries in Southern California, roughly three quarters of the city's land is dedicated exclusively to industrial and commercial uses, including a Chevron oil refinery which alone takes up more than a quarter of the entire city.