Chevron Corporation is an American multinational energy corporation. One of the successor companies of Standard Oil, it is headquartered in San Ramon, California, and active in more than 180 countries. Chevron is engaged in every aspect of the oil, natural gas, and geothermal energy industries, including hydrocarbon exploration and production; refining, marketing and transport; chemicals manufacturing and sales; and power generation. Chevron is one of the worlds largest oil companies; as of 2014[update], it ranked third in the Fortune 500 list of the top US closely held and public corporations and sixteenth on the Fortune Global 500 list of the top 500 corporations worldwide. It was also one of the Seven Sisters that dominated the global petroleum industry from the mid-1940s to the 1970s.