Horn River formed along the middle course of the Horn River, and is followed downstream by the "Second Lake". The river turns south-west, where the "Mink Lake" is formed along its course. The Laferte River also flows into the Mink Lake. Horn River then flows south, and it receives the waters of the Bluefish River before it empties into the Mackenzie River, downstream from the Great Slave Lake), immediately upstream from Mills Lake, at an elevation of . The arch made by the river defines the "Horn Plateau", a flat elevated area that rises up to ) to the north and east,
Mackenzie River north towards the Arctic. It flows through open taiga with its wide valley bounded, on the west, by the Mackenzie Mountains and to the east by low hills of the Canadian Shield. This mostly uninhabited area is called the Mackenzie Lowlands; although partly forested, it is mostly covered by large areas of muskeg, swamps and many small lakes. A number of major tributaries join from the west, including the Root River, Redstone River and Keele River. Below the Keele River, the Mackenzie River flows north along the western base of the Franklin Mountains before turning northwest, and receives the Great