Barnard Castle is for all purposes  located in County Durham. The county boundary with the North Riding of Yorkshire was adjusted in 1967: that part of the town of Barnard Castle historically in Yorkshire was added to County Durham. Barnard Castle was the administrative centre of the former Teesdale district of County Durham until its abolition on 1 April 2009. The town is now administered by Durham County Council Unitary Authority, as principal authority and by Barnard Castle Town Council, as a parish. The Town Council elects a ceremonial Town Mayor annually. It is part of the Bishop Auckland parliamentary constituency, which as of 2017 is represented in parliament by Helen Goodman , though with a small majority over the Conservatives. It is in the North East England region, which serves as a constituency for the European Parliament.  Between 1894 and 1967 the town was administratively part of Barnard Castle Urban District. All four local councilors are Conservative. The local police force is Durham Constabulary. The town is the base for the Barnard Castle division, which covers 300 square miles .  This division is within the force's south area.. What county was Barnard Castle historically located in?