Consists of the journals during the expedition's route from the Vermillion River to Fort Mandan, North Dakota, and their winter encampment there. It describes their encounters with Sioux, Arikara, Mandan, and Hidatsa Indians, including considerable ethnographic material on these tribes. Some miscellaneous documents containing information gathered during the first year of the expedition, originally published in a separate volume, are here brought together in an appropriate chronological sequence.