The Mackenzie River is the second-longest river system in North America after which river?

Discover Canada records this in one direct sentence. The guide writes: The Mackenzie River, at 4,200 kilometres, is the second-longest river system in North America after the Mississippi and drains an area of 1.8 million square kilometres. The river the test wants is therefore the Mississippi.

The Mackenzie's scale is enormous. Discover Canada commits to specific figures: 4,200 kilometres in length, with a watershed of 1.8 million square kilometres. So while only the Mississippi is longer in North America, the Mackenzie surpasses every other Canadian and most American river systems in scale.

The Mackenzie flows through the Northwest Territories. Discover Canada places the Mackenzie River in the Northwest Territories, where its watershed drains a massive portion of northern Canada. The territory is described as "the second-longest river system in North America" — meaning Canadian geography includes one of the world's largest river basins, even if Canadians are more familiar with the St. Lawrence or the Great Lakes.

The Northwest Territories combines the Mackenzie with other distinctive features. Discover Canada writes that "more than half the population is Aboriginal (Dene, Inuit and Métis)." The territory's capital, Yellowknife, is called the "diamond capital of North America." The Mackenzie River is a historic transport route — fur traders, Aboriginal peoples, and modern travellers have used it for centuries. Today the river system supports communities, ecosystems, and resource extraction across one of Canada's most sparsely populated but geographically vast regions. Naming the Mackenzie as the second-longest in North America after the Mississippi places Canadian geography firmly inside the continent's natural-feature record book.

The question is testing whether new citizens know the longest river system in North America (against which the Mackenzie is second). Discover Canada commits to one river: the Mississippi. The right test answer matches that.

The wrong answer choices each pick a different river. The St. Lawrence River is central to Canadian commerce but does not exceed the Mackenzie's length. The Fraser River is in British Columbia, much shorter. The fourth option also flows through the western part of the continent but is not named as longer than the Mackenzie. Only the Mississippi — North America's longest river system — is named in the source.