This book presents a firsthand historical account of life among the Plains Indians during a pivotal era of westward expansion. The author, Francis Parkman Jr., a scion of a wealthy Boston family, details his immersive experience living with a band of Oglala Sioux as they journeyed along the Oregon Trail in the summer of 1847. Parkman's narrative offers a unique perspective on the customs, daily life, and challenges faced by both the Native Americans and the early travelers on this iconic route.

This work is regarded as a significant historical document, offering a rare, personal glimpse into the lives of the Oglala Sioux and the Oregon Trail experience from the mid-19th century. Parkman's detailed observations provide valuable ethnographic data and a vivid portrayal of a culture encountering the encroaching frontier. The narrative's strength lies in its immediacy and the author's dedicated, albeit subjective, engagement with his subjects. It serves as both a historical record and a personal memoir of a transformative period in American history.