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David Thompson was schooled for a career in the Royal Navy; at the end of the Seven Years War, when the navy was downsized, he was apprenticed instead to the Hudson's Bay Company. His first years in the fur trade were spent at the bay and along the North and South Saskatchewan Rivers. At the inland posts he was caught up in the rivalry between the Hudson's Bay Company and Canadian traders who had recently joined together as partners in the North West Company. In 1778–88 the young man went "a full month's march at about fifteen miles a day . . . over a fine country" west– southwest of the river posts in order to trade with "Peeagans" camped along the front ranges. Thompson's rudimentary knowledge of Cree allowed him to converse with Sarka- map-pee, an old man who had personal experience of the Plains tribes' shifting alliances and the smallpox epidemic of 1781. Five years later Peter Fidler, a fellow Hudson's Bay Company apprentice, also wintered with "Peeagans" and served at the Saskatchewan River posts.
A broken leg forced Thompson to winter at Cumberland House, which, he wrote, "by the mercy of God turned out to be the best thing that ever happened to me." He and Fidler studied surveying with Philip Turnor, sent from England to verify claims of Peter Pond's map of Northwest America. Both apprentices became accomplished surveyors and cartographers. But after ten years of routine inland trade Thompson grew impatient to explore and chart beyond the Hudson's Bay Company's trading frontier. In 1797 he left his winter post in the "Rat Country" west of Hudson Bay and joined the North West Company.
In order to regulate their southwest trade, the partners from Canada commissioned Thompson to ascertain the positions of the Missouri and Mississippi headwaters relative to Lake Superior and Lake of the Woods. As of 1792 the forty-ninth parallel had been proposed as the western boundary between British and American territories. This line would replace the earlier treaty of 1783 that agreed on a border along the supposed northerly source of the Mississippi near Lake of the Woods.
Thompson's route for this survey lay south to the Assiniboine River and south again to Turtle Mountain and the Souris River. He and his nine men walked overland in December storms, finding little shelter or wood and few animals to hunt. The only advantage to traveling so late in the season was a lowered risk of running into "Sieux," who would have opposed their trade with the "Mandanes." On December 30, 1797, Thompson arrived at the first of five villages of "Mandanes" and "Willow" or "Fall Indians" located near the junction of the Missouri and Knife Rivers. He stayed for two weeks, long enough to map the region, compile a vocabulary, and inquire how the hundreds of domed houses were built. Thompson wrote that his time was "spent in noticing their Manners and conversing about their Policy, Wars, Country, Traditions, &c &c." Watchful for the interests of the North West Company, he concluded that "no hopes could be entertained of their ever coming to our Settlements to Trade–indeed they seem to have but little that is valuable to us." Nothing in this remark indicates awareness of the importance of the villages in a longdistance network of Native trade. In 1803 Samuel King would use Thompson's survey of this region as well as Fidler's information on the upper Missouri to draw a map for Lewis and Clark. The American explorers wintered at the "Mandane" villages in 1804–5.
Soon after his return to the Assiniboine River in the spring of 1798, Thompson set out again to discover the source of the Mississippi, which he identified as "Turtle Lake in Latitude 47.39.15 N Longitude 95.12.45 W." As Thompson explained, the supposition of a more northerly source was due to "the Fur Traders . . . counting every pipe a League of three miles at the end of which they claimed a right to rest and smoke a pipe. By my survey I found these pipes to be the average length of only two miles, and they also threw out of account the windings of the River." This location, while not exact, at least placed the Mississippi well south of Lake of the Woods and was crucial in promoting the forty-ninth parallel as the international boundary across the Plains.
Unlike these two trips of 1797–98, Thompson's later explorations west of the continental divide were once more subordinated to his role of trader. From 1807 to 1812 Thompson worked to establish a new fur-trade department between two Rocky Mountain passes and the mouth of the Columbia River. He also surveyed this region, later incorporating his regional charts into three huge manuscript maps of the continent from Hudson Bay and the Great Lakes to the Pacific Ocean. The historical construction of a "race to the sea," which places Thompson a poor third behind the Corps of Discovery and the Astorians, misreads Thompson's fur-trade role and his most important contribution to western exploration: his patient, meticulous mapping of the Columbia River from source to sea.
Thompson retired from the fur trade in 1812 but continued survey work for the international border along the Great Lakes and in Lower Canada. His hope of a comfortable settled life vanished with poor investments; he was still camping with survey crews when he was well past sixty years of age. In 1845 he began a commentary on his years in the fur trade, based on the journals he had kept during that period. The fluent, poetic style of this text has made it a favorite among exploration accounts since its publication in 1916. Some of his journals have also been edited: these terse, detailed, professional records are of great interest to regional and fur-trade historians.
See also: POLITICS AND GOVERNMENT:
Forty-ninth Parallel.