 At dissolution it was the most populous rural district council in Kent, but had once been larger, having lost territory when Crayford Urban District was created in 1920, and Swanscombe Urban District in 1926.On 1 April 1974 it was split between the borough of Dartford and the new district of Sevenoaks.The civil parishes of Ash-cum-Ridley, Eynsford, Eynsford-Crockenhill, Farningham, Fawkham, Hartley, Horton Kirby, Swanley, and West Kingsdown, all of which became part of Sevenoaks District, are sometimes still collectively referred to as the 'Northern Parishes'.