Since the time of Columbus, explorers dreamed of a water passage across the North American continent. President Thomas Jefferson shared this dream. He conceived the Corps of Discovery to travel up the Missouri River to the Rocky Mountains and westward along possible river routes to the Pacific Ocean. Meriwether Lewis and William Clark led this expedition of 1804–6. Along the way they filled hundreds of notebook pages with observations of the geography, Indian tribes, and natural history of the trans-Mississippi West.

This complete set of the celebrated Nebraska edition incorporates the journals along with a wide range of new scholarship dealing with all aspects of the expedition, including geography, Indian languages, plants, and animals, in order to recreate the expedition within its historical context.