The capital is Augusta. About half of Maine’s residents live in what are classified as urban centres, but there are only three cities with more than 25,000 people. Most of the urban centres lie within the Maine Corridor. Maine’s largest urban areas are those of Portland–South Portland–Biddeford, Lewiston-Auburn, Bangor, and Augusta-Waterville. Portland is the centre of a metropolitan area spreading inland from and around Casco Bay. It is the commercial and transportation hub of the state, and its economy has a growing and diversified industrial base. Biddeford, south of Portland, is a former major textile centre. Once an important textile and shoe manufacturing centre, the twin cities of Lewiston and Auburn form the second largest urban area in the state. Today the area depends on diversified manufacturing and is an important commercial hub that serves both the Androscoggin valley and eastern Oxford county. Bangor, an old lumbering town at the head of navigation on the Penobscot River, is the commercial focus of a large hinterland which includes northern and eastern Maine. Augusta, the state capital, lies at the head of navigation on the Kennebec River. State government is its principal source of employment, but the city is also an important trade centre for west-central Maine. Waterville, north of Augusta on the Kennebec, together with its neighbouring communities of Winslow and Fairfield, experienced reverses in the manufacturing sector in the late 20th century. The urban area is home to smaller and more-diverse industries and is, like Augusta, a regional trade centre.