Durham

Administrative, geographic, and historic county in northeastern England on the North Sea coast. It comprises two upland regions, lowlands of Wear valley, and limestone plateaus. The administrative county comprises seven districts: Chester-le-Street, Derwentside, the city of Durham, Easington, the borough of Sedgefield, Teesdale, and Wear Valley. The geographic county includes the entire administrative county, the unitary authorities of Darlington and Hartlepool, and the part of the unitary authority of Stockton-on-Tees (including the historic core of Stockton) north of the River Tees. The historic county includes the entire geographic county except for the part of the Teesdale district south of the River Tees, which belongs to the historic county of Yorkshire. The metropolitan boroughs of Gateshead, South Tyneside, and Sunderland in the metropolitan county of Tyne and Wear also belong to the historic county of Durham. The region was inhabited by agricultural peoples from Neolithic times through the Iron Age. Durham was incorporated into the Saxon kingdom of Northumbria during the 6th century. The region became important economically when it became a center for coal-mining and other heavy industry in the 19th century. Durham county was the site of the world's first passenger railway, which began running between Stockton and Darlington in 1825. The county suffered economic depression between World Wars I and II.