The River Tees is a major river in northern England. It rises on Cross Fell in Cumbria and flows through County Durham, north Yorkshire and Cleveland before entering the North Sea at Redcar. In its upper reaches it flows through the upland country of the North Pennines. Its middle reaches flow through agricultural countryside. The lower reaches of the Tees - from Stockton on Tees to the sea pass through a heavily industrialised landscape. Teesside (Stockton, Thornaby, Middlesbrough and neighbouring settlements) was the site of coal export facilities, shipbuilding, chemicals manufacture and iron and steel making; and chemicals and steel are still the industrial mainstay of the area.