Marathon Oil Corporation is an American company engaged in hydrocarbon exploration incorporated in Ohio and headquartered in the Marathon Oil Tower in Houston, Texas. A direct descendant of Standard Oil, it also runs international gas operations focused on Equatorial Guinea, offshore Central Africa. The company is ranked 534th on the Fortune 500 and 1900th on the Forbes Global 2000. As of December 31, 2020, the company had of estimated proven reserves, of which 86% was in the United States and 14% was in Equatorial Guinea. The company's proved reserves consisted 52% of petroleum, 30% natural gas and 18% natural gas liquids. In 2020, the company sold per day, of which 26% was from the Eagle Ford Group, 27% was from the Bakken formation, 17% was from Oklahoma, 7% was from the Northern Delaware Basin, 2% was from other U.S. sources, and 20% was from Equatorial Guinea. History Marathon Oil began as "The Ohio Oil Company" in 1887. In 1889, the company was purchased by John D. Rockefeller's Standard Oil. It remained a part of Standard Oil until Standard Oil was broken up in 1911. In 1930, The Ohio Oil Company bought the Transcontinental Oil Company and established the "Marathon" brand name. In 1962, the company changed its name to "Marathon Oil Company". In 1981, Mobil made a hostile takeover offer to buy the company. However, the board of Marathon Oil rejected the offer and instead sold the company to United States Steel. A legal battle ensued thereafter. In 1990, the headquarters was moved to Houston, Texas, but the company's refining subsidiary maintained its headquarters in Findlay, Ohio. In 1984, Marathon purchased the U.S. unit of Husky Energy for $505 million. In 1998, Marathon and Ashland Global contributed their refining operations to Marathon Ashland Petroleum LLC, now Marathon Petroleum. In 2001, USX, the holding company that owned United States Steel and Marathon, spun off the steel business and, in 2002, USX renamed itself Marathon Oil Corporation. In 2003, Marathon sold its Canadian operations to Husky Energy. In 2003, the company sold its interest in the Yates Oil Field to Kinder Morgan for $225 million. In 2007, Marathon acquired Western Oil Sands for $6.6 billion and gained ownership of its 20% stake in the Athabasca oil sands in northern Alberta and other assets in the midwestern United States. In 2011, Marathon completed the corporate spin-off of Marathon Petroleum, distributing a 100% interest