The Tees is a river in Northern Englan. It rises on the eastern slope of Cross Fell in the Pennines, and flows eastwards for about 85 miles (132 km) to the North Sea, between Hartlepool and Redcar. It drains an area of 708 square miles (1834 square km), and subsumes no important tributaries. The river formed the boundaries between the historic counties of County Durham and Yorkshire. At its lower reaches it now forms the boundary between the ceremonial counties of County Durham and North Yorkshire.