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 and was consulted for information on them by several noted investigators of Indian culture. When Denig was asked to respond to a circular by Henry Rowe Schoolcraft, he didn&;t simply rely on his own knowledge of the Assiniboines, but instead interviewed his subjects "for an entire year, until satisfactory answers [had] been obtained."

Denig&;s manuscript, which he probably finished in 1854, remained unpublished until 1930, when J. N. B. Hewitt edited it for publication in the Smithsonian Bureau of American Ethnology&;s Forty-sixth Annual Report. This edition, featuring an introduction by David R. Miller, provides a complete ethnology of the Assiniboine Indians, including information on their history, tribal organization and government, religion, manners and customs, warfare, dances, and language.