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Artist conception of David Thompson, 2005
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“Many of the observations in this book were taken and entered in so hasty a Manner… parts of my journal are, I am afraid, to be understood by none but myself.”
Entry dated 24 November 1797, Journal #5 David Thompson’s notebooks and journals Reference Code: F 443-1 Archives of Ontario
Journal No. 25, p. 88 (1810-1812)
David Thompson’s notebooks and journals
Reference Code: F 443-1
Archives of Ontario
Thompson retired from the fur trade in 1812 and moved his family to Terrebonne near Montreal. He was given a special assignment to plot all the Company’s posts on a comprehensive map of the Canadian West using the astronomical observations he had carefully recorded.
Thompson’s great map of the “North-West Territory . . . of Canada” is approximately 213 centimetres (84") high by 328 centimetres (129") long. It gave an accurate depiction of the vast territory traversed by the fur trade and location of Company posts.
An earlier version of this map hung in the North West Company headquarters at Fort William.
The Treaty of Ghent, which ended the War of 1812, required a formal survey of the Canada – United States border. Appointed official astronomer and surveyor to the British Commission in 1816, Thompson travelled and mapped some 1600 km (1,000 miles) between St. Regis near Cornwall to Lake of the Woods near Kenora.
Following his work for the Boundary Commission, Thompson completed various survey projects including the border between Upper and Lower Canada and a canal scheme between Lake Huron and the Ottawa River.
Using a sextant, transit, theodolite and other surveying equipment, Thompson established fixed reference points to calculate precise distances and locations for the border survey.
The drawing below by William Jefferys portrays David Thompson taking an observation of the sun to enable to him to determine his location.
The contemporary photograph to the right, taken near Pointe-Fortune, Quebec, shows the boundary marker between Upper and Lower Canada as established by Thompson.