The English administration in Ireland in the years following the Anglo-Norman invasion of Ireland created counties as the major subdivisions of an Irish province. This process lasted a period from the 13th to 17th centuries; however, the number and shape of the counties that would form the future Northern Ireland would not be defined until the Flight of the Earls allowed the shiring of Ulster from 1604. Each county would have an associated county town, with county courts of quarter sessions and assizes.