The 39 km (24 mi) stretch from Enterprise to Hay River is Northwest Territories Highway 2.

Around 1970, the highway was extended west from what is now the southern terminus of Highway 3 to reach Fort Simpson, and in 1971, when the section to Fort Simpson was opened to traffic, work began to prepare a road grade from there to Wrigley, but the work was abandoned.

[2] There are social and economic studies being done on the extension of the highway north from Wrigley to join the Dempster Highway; the territorial government has completed 34 bridges across all but six of the widest river crossings that serve the ice road and await the all-weather route.

[3] In June 2018, an announcement of $140 million funding would result in a bridge over Great Bear River and extend the Mackenzie Highway's all-weather road north by 15 km to Mount Gaudet.

[4] Just east of Fort Simpson's airport, the highway crosses the Liard River by ferry (summer) and ice bridge (winter).