Penobscot River

River in central and west Maine; length 563 km/350 mi (from the source of its longest headstream). It follows a mainly southerly and southeasterly course, and empties into Penobscot Bay. With a basin occupying an area of 22,000 sq km/8,500 sq mi, the Penobscot is the most extensive river system in the state. The river is a major source of hydroelectric power, and is navigable as far as Bangor.

The West Branch of the Penobscot (length 177 km/110 mi) and its shorter East Branch join at Medway to flow past Old Town, Orono, and Bangor. The explorer Samuel de Champlain was the first European to explore the river, in 1604, and it soon gained a reputation for excellent salmon fishing. In the 19th century, it became one of the world's leading rivers for transporting lumber. River logging died out by the mid-20th century, since when the Penobscot has gradually regained some of its former tranquillity.