ConocoPhillips Corporate Headquarters, Texas

ConocoPhillips is the fifth largest of the six, non-state owned supermajor oil companies of the world (the others are ExxonMobil, Chevron, BP, Shell, and Total), and the only supermajor based in Houston. It was created by the merger of two already large and established companies, Conoco Inc. and Phillips Petroleum Corporation, in 2002. The company is involved in upstream and downstream operations, from exploration and field development, to refining and branded gas retail sales (through Union 76, Phillips, and Conoco gas stations). In 2012, ConocoPhillips split off their downstream businesses to form a new, independent company called Phillips 66.  As of 2013, Conoco Phillips is the largest producer in Alaska, and part-owner of the Alaska Pipeline. It operates 12 refineries in the United States, making it the second largest capacity refiner in the country.