Edwin Thompson Denig, for more than twenty years a fur trader on the Upper Missouri and married to an Assiniboine woman, was an acute and objective observer of Indian manners and customs. He assisted Audubon and the Culbertsons in collecting Missouri River fauna, supplied information on the Indians to Father De Smet, who encouraged him to write, and provided Henry Schoolcraft with an Assiniboine vocabulary as well as a detailed "Report on the Indian Tribes of the Upper Missouri," which was not published until 1930, seventy-six years after it was written, and then only in parts.

Denig’s writings on the Sioux, Arickaras, Assiniboines, Crees, and Crows, comprising the Denig manuscript in the Missouri Historical Society, are published together for the first time in this book. The manuscript long had been referred to as the "Culbertson Manuscript" because it had been purchased from a descendant of the fur-trader naturalist Alexander Culbertson. But in 1949, handwriting experts identified it as the work of Denig.