David Thompson was one of North America's greatest explorers and mapmakers. His expertise reached from Lake Superior west to the Pacific Ocean, and from Lake Athabasca south to the Missouri. Several years after joining the Hudson's Bay Company (HBC) at age14, he was sent inland to posts on the Saskatchewan River. In 1787-88, he wintered with the Peigan in southern Alberta, where Saukamappee, an adopted Cree, taught him the history of the northern plains: tribal battles, the first horses, the introduction of guns, and the devastating 1781-82 smallpox epidemic. In 1789, while recuperating from a broken leg at Cumberland House, both he and Peter Fidler were taught mapping skills by Philip Turnor. Over the years both men separately surveyed almost identical river systems. Suddenly, while at Reindeer Lake in 1797, Thompson left the HBC to join the North West Company. Much of his fifteen-year career with the NWC was spent outside of Saskatchewan, mostly in the far west where he explored routes through the Rockies and to the Pacific. After retiring to the east in 1812, Thompson drew his famous map of the North-West. He also formally married his Métis wife, Charlotte Small, whom he had met in 1799 at Ile-à-la-Crosse. By 1840, through poor business ventures, Thompson was reduced to poverty. Infirm and growing blind, he tried unsuccessfully to earn money from writing an account of the west. In 1916, the sprawling manuscript was edited for publication. His complete manuscript, a final 1843 map, and almost all his many field books remain unpublished.