 The current borough boundaries were formed on 1 April 1974, by the creation of a new non-metropolitan district of Darlington by the Local Government Act 1972, covering the previous county borough of Darlington along with nearly all of Darlington Rural District (the Newton Aycliffe parts of which went to Sedgefield).It remained part of County Durham for administrative purposes until reconstituted as a unitary authority on 1 April 1997.For ceremonial purposes it remains part of County Durham, with whom it continues to share certain local services, such as Fire and Rescue and Police.