Eddyr 1974 as 1996, rere'n Local Government Act 1972, va De Morgannwg ny choontae jeh daa slyst (Cayr Deeth as Bro Morgannwg).  Hie eh er astyrt, marish y choyrle choontae, er 1 Averil 1996.  Rheynn eh erash dys Cayr Deeth as Bro Morgannwg.