Peace, river, 945 mi (1,521 km) long, formed by the junction of the Finlay and Parsnip rivers at Williston Lake, N central British Columbia, Canada. It flows east through the Rocky Mts., then generally northeast across N Alberta and onto the Northern Plains where it meanders to the Slave River at Lake Athabasca. From the head of the Finlay River the Peace River is 1,195 mi (1,923 km) long; it is one of the chief headstreams of the Mackenzie River. At the mouth of the Peace River is Wood Buffalo National Park. The valley of the middle Peace is fertile, with wheat the chief crop; it is the northernmost commercially important agricultural region of Canada. Large natural gas reserves are tapped along the river; oil, coal, salt, and gypsum deposits are also worked. Near Hudson Hope, British Columbia, W. A. C. Bennett Dam (625 ft/191 m high; opened 1967) impounds Williston Lake (680 sq mi/1,761 sq km). The dam's power plant (present generating capacity 2.1 million kW), the sixth largest in Canada, provides electricity for Vancouver. The Peace River was probably visited (1775–78) by Peter Pond, the American fur trader, and first explored (1792–93) by Sir Alexander Mackenzie, the Canadian explorer. It was long an important route of fur traders. Settlement in the valley began in the early 1900s.