The following outline is provided as an overview of and topical guide to Cornwall:Cornwall – ceremonial county and unitary authority area of England within the United Kingdom. Cornwall is a peninsula bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall is also a royal duchy of the United Kingdom. It has an estimated population of half a million and it has its own distinctive history and culture.