Archaeological survey in northwestern Saskatchewan identified sites ascribable to three resident ethnic/cultural groups: Chipewyan Indians, Cree/Metis Cree Indians and Euro—Canadians. Emphasis was placed on recording 19th and early 20th century sites, which are under-reported in the archaeological literature for the area. Archaeology, informant testimony and on—site interpretation of features, and ethnoarchaeological research on contemporary communities were combined to study ecological adaptations of the three populations and to define archaeological site formation processes. Each population adapted to the fur trade and to the other populations by filling specialized roles or occupations within the new mercantile system. Evidence for these different adaptations is discussed.