Cornwall Cornish: Kernow Latin: (Cornubia or Cornuvia) is a unitary authority and ceremonial county of England, within the United Kingdom. It is 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 has a population of 537,400 and covers an area of 3,563 km (1,376 sq mi). The administrative centre and only city is Truro. The area now known as Cornwall was first inhabited in the Palaeolithic a...