 It comprised the parishes of Bedwas, Bettws, Coedkernew, Duffryn, Graig, Henllys, Machen Lower, Machen Upper, Malpas, Marshfield, Michaelstone-y-Fedw, Peterstone Wentloog, Rogerstone, Rumney, St Brides Wentloog, St Mellons and St Woolos in the administrative county of Monmouthshire.Initially, the St Mellons Rural District Council also administered two parishes in Glamorgan