The County Palatine of Durham and Sadberge, commonly referred to as County Durham or simply Durham, is a historic county in Northern England. Until 1889, it was controlled by powers granted under the Bishopric of Durham. The county and Northumberland are also traditionally known together as Northumbria. The boundaries stretch between the rivers Tyne and Tees. It borders four counties: Northumberland to the north, Yorkshire to the south as well as Westmorland and Cumberland to the west. Settlements with the most population in the county are Sunderland, Gateshead and Darlington.