town and district, administrative and historic county of Durham, England, at the southern edge of the Tyne and Wear metropolitan area near the River Wear. It was the site of a Roman station behind the frontier of Hadrian's Wall, a defensive barrier erected across northern Britain as protection against raids from what became Scotland. The modern development of the town dates from the 17th century, when it began to grow as a centre for the local coal-mining settlements. With the closing of the mines, the district is now mainly residential. Area 26 square miles (68 square km). Pop. (2001) town, 36,049; district, 53,694.