In 1789, Alexander Mackenzie traveled 1200 miles on the immense river in Canada that now bears his name, in search of the fabled Northwest Passage that had eluded mariners for hundreds of years. In 2016, the acclaimed memoirist Brian Castner retraced Mackenzie's route by canoe in a grueling journey -- and discovered the Passage he could not find.

In 1789, Alexander Mackenzie traveled 1200 miles on the immense river in Canada that now bears his name, in search of the fabled Northwest Passage that had eluded mariners for hundreds of years. In 2016, the acclaimed memoirist Brian Castner retraced Mackenzie's route by canoe in a grueling journey -- and discovered the Passage he could not find.