Seven large, vertically integrated oil companies dominated the world oil industry from the 1920s to the 1970s. With annual sales in the billions of dollars, the so-called "seven sisters" have consistently ranked among the largest industrial companies in the world. The five American international major oil companies were Standard Oil Company (New Jersey), which became Exxon in 1972; Socony-Vacuum Oil Company, which became Socony Mobil in 1955 and Mobil in 1966; Standard Oil Company of California, later Chevron; the Texas Company, which became Texaco in 1959; and Gulf Oil Company. Chevron bought Gulf in 1984, and in 1998 Exxon and Mobil merged to form Exxon-Mobil.
The other two international majors were Anglo-Persian Oil Company, which changed its name to Anglo-Iranian in 1935 and to British Petroleum in 1954, and the Royal Dutch/Shell group. The British government held a majority share in British Petroleum from 1914 to the 1980s, when Margaret Thatcher's government sold its shares to private investors. Although ownership was divided between Dutch (60 percent) and British (40 percent) interests, Shell had its operating and commercial headquarters in London and was regarded as a British company.