Some of the world's biggest oil companies are based in the United States, such as ExxonMobil Corporation, ConocoPhilips and Chevron Corporation. The country is home to over 100 oil and gas companies in total.
ExxonMobil was created in 1999 through a merger of the Exxon and Mobil corporations. Exxon grew out of Standard Oil of New Jersey, while Mobil originated from Standard Oil of New York. ExxonMobil is also one of the world's largest companies by revenue and also markets gas around the world under the brand name Esso.
ConocoPhillips was also created via merger of two major oil companies, Conoco Inc. and Phillips Petroleum Co., in 2002. The company is headquartered in Houston.
Chevron Corporation is a descendant of Standard Oil of California. In 1948, the company discovered the world's largest oil field in Saudi Arabia. Over time, the Saudis bought out ownership of it, eventually taking complete control in 1980. Chevron acquired Texaco in 2000 and still uses the brand name in some markets.
Some other major oil companies based in the United States include Anadarko Petroleum Corporation, Devon Energy Corporation, Occidental Petroleum Corporation, Marathon Oil Corporation and Hess Corporation. Many of the major oil companies in the United States are headquartered in Houston.