On its creation in 1918 the constituency consisted of the urban districts of Bedwas and Machen, Bedwellty, Mynyddislwyn and Risca and the civil parish of Rogerstone in St Mellons Rural District.
In 1918, the constituency comprised the urban areas of Bedwas and Machen, Bedwellty, Mynyddislwyn, and Risca, along with the civil parish of Rogerstone in St Mellons Rural District.