George Amos Dorsey was an U.S. ethnographer of Indigenous peoples of the Americas, with a special focus on Caddoan and Siouan tribes. He received a Bachelor of Arts degree from Denison University in 1888, then a second Bachelor's Degree in anthropology in 1890 at Harvard university, and finally PhD in 1894, the first PhD in anthropology from Harvard, and the second ever awarded in the United States. The following account of the Cheyenne social organisation was obtained as part of Dorsey's studies of the Cheyenne Sun-Dance, which, in turn, are part of a comparative study on this ceremony among the Plains Tribes he began in 1901. The Cheyenne Sun-Dance forms the subject of Part II. The accounts of the societies, the myths of the origin of the same, and the story of the medicine-arrows are given, with but slight changes, as they were obtained through Richard Davis, a full blood Cheyenne.