Sunoco is an American petroleum and petrochemical manufacturer headquartered in Philadelphia, Pennsylvania, formerly known as Sun Company Inc.. In Canada, Sunoco is operated by Suncor Energy, a separate Canadian entity. Sunoco is a Fortune 100 Company. It is also the biggest company based in Philadelphia and the 2nd biggest in Pennsylvania behind AmerisourceBergen. History The integrated oil company now known as Sunoco began as The Peoples Natural Gas Company in Pittsburgh, Pennsylvania. In 188… (More on Sunoco)