David Thompson’s Map of Lake Superior

David Thompson retired from the North West Company (NWC) in 1812. Over the next four years, he occupied himself with creating maps of his explorations for himself and the NWC. Following the signing of the Treaty of Ghent, ending the War of 1812, John Oglivy was assigned to be the Commissioner of Articles 6 and 7 of the treaty which stated that a boundary was to be determined between US and British Territory. As a former North West Company partner, Ogilvy knew Thompson, and he would have been aware of Thompson’s 1798 near circumnavigation to survey Lake Superior and had likely seen the first accurate maps of Superior made of that survey. Consequently, Ogilvy’s familiarity with Thompson’s experiences led Ogilvy, in October of 1816, to choose David Thompson as Astronomical Surveyor to the commission for Articles 6 and 7 of the treaty.

The survey effort of both the Americans and British began in earnest in 1817 and by 1821 and progressed as far as Sault Ste Marie. On 28 June 1822, Thompson began his survey of Lake Superior and completed it in the morning of 27 July. Maps were created of the entire survey between Cornwall and Lake Ontario over a period of 10 years including individual maps of the Lake Superior survey. Thompson’s proficiency at his chosen trade was exceptional given the testimony of his contemporaries. When David Adams resigned his office as the principal American Surveyor in 1819, he informed the American Commission that until such time a suitable replacement could be found, they could rely on “… the Latitudes and Longitudes resulting from the observations of David Thompson… a gentleman whom from his… abilities in his profession, I shall hold in the highest estimation.” This is a remarkable statement, given that the American survey effort was a military operation, and Adams effectively advised his superiors to rely on their former adversary to create official American survey information.

A reduced version of this map has been created with a dimension of 80.5 x 45 cm (31.75 x 17.75 inches) at 300dpi that is suitable for study and can be acquired HERE.

See Image Gallery below for image quality example.