This picture is of Whirling Horse. I consider this photograph to be a classic, and shows the man with full head dress, buckskin clothing, and blanket. It is believed that Whirling Horse was a member of a Wild West Show, possibly Buffalo Bill Cody's. So, in looking at the picture we must wonder whether this is the way he looked as a traditional Indian person, or whether this is how Buffalo Bill told him he should dress for the show.
Sioux Chief Sitting Bull - Sioux, or Dakota, Indians, a large and powerful tribe of Indians, who were found by the French, in 1640, near the headwaters of the Mississippi River. The Algonquiens called them Nadowessioux, whence they came to be called Sioux. They occupied the vast domain extending from the Arkansas River, in the south, to the western tributary of Lake Winnipeg, in the north, and westward to the eastern slopes of the Rocky Mountains.
North American Indian Tribes of the Great Lakes (Paperback)