The historic boundaries of County Durham included a main body covering the catchment of the Pennines in the west, the River Tees in the south, the North Sea in the east and the Rivers Tyne and Derwent in the north. The county palatinate also had a number of liberties: the Bedlingtonshire, Islandshire and Norhamshire exclaves within Northumberland, and the Craikshire exclave within the North Riding of Yorkshire. In 1831 the county covered an area of and had a population of 253,910. These exclaves were included as part of the county for parliamentary electoral purposes until 1832, and for judicial and local-government purposes until the coming into force of the Counties (Detached Parts) Act 1844, which merged most remaining exclaves with their surrounding county. The boundaries of the county proper remained in use for administrative and ceremonial purposes until the 1972 Local Government Act.