Formerly, the main unit of local administration in England. Shires evolved as territorial units in Wessex in the 9th century, replacing the Roman system of provinces. They were extended over a wider area of England by Alfred the Great and his heirs as administrative and political units. The English shire system reveals many different evolutionary processes. Some were based on former kingdoms (Kent, Sussex, Essex); others on tribal subdivisions within a kingdom (Norfolk and Suffolk); others were created during the 10th-century reconquest of the Danelaw or as territories centred on towns (Oxfordshire, Warwickshire, Buckinghamshire, etc.). England north of the River Tees was not absorbed into the shire system until the Norman Conquest when shires were restyled ‘counties’.