Mackenzie River Mackenzie River, in the Northwest Territories, is the longest river in Canada. Water flows into the Mackenzie from many tributaries, including the Liard, Great Bear, Arctic Red, and Peel rivers.
Water also enters from Great Slave Lake.
It reaches the lake through the Slave River, which collects water from the Peace and Athabasca rivers. All the rivers mentioned above are part of the Mackenzie River System, Canada's largest river system. In North America, only the Mississippi-Missouri system in the United States is longer than the Mackenzie system. Barges carry cargo over much of the Mackenzie River system. The Mackenzie River basin is rich in natural resources.