Scottish-born Alexander Mackenzie (1763-1820) entered the fur trade and from 1788 to 1796 commanded Fort Chipewyan on Lake Athabasca in present-day Alberta for the North West Company. During this time he made voyages to the Arctic and Pacific oceans. Between these explorations he went to England to learn navigational science. In 1801 he returned to England to publish Voyages from Montreal, on the River St. Laurence, through the Continent of North America which chronicled his exploits in western Canada. After being knighted for his achievements in exploration, Mackenzie acted as a statesman in urging Britain to assert control over the Pacific Northwest.
Mackenzie was the second explorer to reach Lake Athabasca and the Great Slave Lake. Mackenzie not only followed the American Peter Pond to Lake Athabasca, he also based his route to the Pacific on Pond’s prediction that a river led from the Great Slave Lake to the Pacific Ocean. In 1789, when Mackenzie followed this river (which later bore his name), he reached instead the Arctic Ocean. Four years later he ascended the Peace River before crossing over the Continental Divide to the Fraser River— a river which he believed to be the upper reaches of the Columbia River and labeled the “Tacoutche Tesse or Columbia River” on his map. Mackenzie completed his journey in July 1793 by traveling over land another fourteen days to the Pacific Ocean at present-day Bella Coola, British Columbia. Mackenzie thus became the first European to reach the Pacific coast north of Mexico by traveling from the east.
Thomas Jefferson was aware of Mackenzie’s success at least as early as 1797, although he did not read the detailed account of the voyage until the summer of 1802. Jefferson’s attention doubtlessly would have been drawn to Mackenzie’s description of an easy crossing of the Continental Divide. Mackenzie’s claim that he traveled on a path that was only “eight hundred and seventeen paces in length over a ridge of 3000 ft. elevation” and his report that the mountains to the south were of even lower elevation, convinced Jefferson of the feasibility of an American expedition across the continent. Moreover, Mackenzie’s urgent recommendations that the British government secure control of the Pacific Northwest probably also hastened President Jefferson’s authorization of an expedition to the Northwest.