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 is scant, despite the efforts of many researchers. Many archaeological sites have probably been destroyed by flooding, freeze-thaw and erosion. The Inuvialuit, Gwich'in and other indigenous peoples have lived along the river for thousands of years; however, the oldest evidence of continuous occupation stretches back only about 1300–1400 years, at the Gwich'in community of Tsiigehtchic. The Mackenzie provided the major route into Canada's northern interior for European explorers as early as the late 18th century. Scottish explorer Alexander Mackenzie travelled the river in the hope it would lead to the Pacific Ocean, but instead reached its mouth on the Arctic