While originally devised by the Boundary Commissioners in 1885, the division was originally named as 'Birstal', "from the name of a large ancient parish" [REF].
When redefined by the Boundary Commission in 1917, the county division was defined as consisting of the Urban Districts of Birkenshaw, Birstall, Drighlington, Gildersome, Heckmondwike, Hunsworth, Kirkheaton, Lepton, Mirfield, Spenborough and Whitley Upper [REF].