The book begins with the letter to Clark proposing a "trip to explore those western rivers which may run all the way across North America to the western ocean" and Clark's reply "to cheerfully join you in this rewarding endeavor." From there, every stage of the journey is shown - from the building of the ships the crew would use, the choosing of the crew itself, and the farewell from St. Louis on May 14, 1804 to meetings with friendly and unfriendly Indian tribes, discovering a wealth of previously unknown plants and animals, bouts with fleas and fever, a miserable climb through the Bitterroot Mountains, and finally the much-longed-for view of the Pacific Ocean. The text is taken directly from the journals of Lewis and Clark, which makes it excellent primary source material. In addition, every page is filled with illustrations in a charming folk-art style that bring the scenes to life.