David Thompson
Thompson, David (1770–1857), a Canadian geographer and explorer. With remarkable accuracy he surveyed and mapped vast wilderness areas of western North America.
Thompson was born in London and was educated at a charity school. He went to Canada in 1784 as an apprentice of the huge British fur trading organization, the Hudson's Bay Company. There he learned the craft of surveying. In 1797–98, as an agent of the North West Fur Company, Thompson surveyed the land around the headwaters of the Mississippi River and discovered one of the river's sources. From 1807 to 1811 he explored the Columbia River area, in 1811 traveling the river from where it enters the Pacific to its source at Columbia Lake. He helped survey the Canadian-United States border, 1816–26.