The kingdom of the West Saxons founded by Cerdic in the upper Thames Valley c 494/495 AD and from another site, known only from archaeological evidence, situated on the upper Thames and was probably settled from the northeast. Wessex first spread in influence to the south and west and was one of the last Anglo-Saxon kingdoms to become firmly established. Its nucleus approximated that of the modern counties of Hampshire, Dorset, Wiltshire, Somerset, and southern Avon. At times its land extended north of the River Thames, and it eventually expanded to cover Devon and Cornwall. It reached its peak in the 9th century. Wessex under Alfred (871-899) became the nucleus of a unified England.