Berwick-upon-Tweed , former district, Northumberland, NE England, at the mouth of the Tweed River. The district includes the Holy Islands and the Farne Islands and extends SW to the Cheviot Hills. The town of Berwick, located in the former district, is a market town and seaport, famous for its salmon fishing. Grain is the chief export; oil and timber are imported. Industries include shipbuilding, engineering, sawmilling, fertilizer production, and the manufacture of tweed and hosiery. The principal border town between Scotland and England, Berwick changed hands more than 13 times between 1147 and 1482, when Edward IV finally claimed it for England. It did not become officially English until 1885. Of interest are the Royal Border Bridge, the old barracks, and the walls surrounding the city that were especially designed to utilize artillery guns. Berwick-upon-Tweed was abolished as a local government authority in 2009 when Northumberland became a unitary authority.