Wikipedia
Premcor
Premcor (formerly NYSE symbol PCO) was a Fortune 500 oil refinery group based in Greenwich, Connecticut. It operated five refineries, which are located in Port Arthur, Texas; Memphis, Tennessee; Lima, Ohio; Hartford, Illinois; and Delaware City, Delaware with a combined crude oil volume processing capacity of approximately (July, 2007).
Premcor was acquired by Valero in 2005. Valero would later sell the Lima facility to Husky Energy in July 2007 and close the Delaware City refinery in November 2009.