David Thompson (1770-1857) was born at Westminster, London, on 30 April 1770, and educated at Grey Coat School, Westminster. He was apprenticed to the Hudson's Bay Company in 1784, and was employed as a clerk at Hudson Bay and in the interior. He joined the North West Company in 1797, becoming a partner, and worked in the fur trade until 1812. During this period, Thompson undertook exploratory expeditions, during which he mapped the terrain and became the first white man to descend the Columbia River from its source to its mouth. He was engaged on surveying the boundary between Canada and the United States from 1816 to 1826, and subsequently worked on other surveys. He died at Longueuil, near Montreal, on 10 February 1857.