 When Castleton Urban District was absorbed in 1900, an eleventh ward of Castleton Moor was added, and the council increased to thirty-three councillors and eleven alderman.In 1933 the bulk of Norden Urban District was added to the borough as a twelfth ward, and the council consisted of thirty-six councillors and twelve aldermen until its abolition in 1974.For the first seven decades of the borough's existence it was dominated by the Liberal Party, who maintained a large majority.