This new edition of the classic volume The Assiniboine, with an introduction by David R. Miller, provides a complete ethnology of the Assiniboine Nation, including information on their history, tribal organization and government, religion, society, warfare, dances, and language. Edwin Thompson Denig entered the fur trade on the Upper Missouri River in 1833. As husband to the daughter of an Assiniboine headman and as a bookkeeper stationed at Fort Union, Denig became knowledgeable about the tribal groups of the Upper Missouri. By the 1840s and 1850s, several noted investigators of Indian culture were consulting him, including Audubon, Hayden, and Schoolcraft. Not content to draw on his own knowledge, he interviewed in company with the Indians for an entire year until he had obtained satisfactory answers. Denig's manuscript was unpublished until 1930, when J.N.B. Hewitt edited it for publication in the Smithsonian Bureau of Ethnology's Forty-sixth Annual Report. The report, long unavailable, is reprinted here for the first time.