Includes Lewis's and Clark's journals for the period from August 1803, when Lewis left Pittsburgh to join Clark farther down the Ohio River, to August 1804, when the Corps of Discovery camped near the Vermillion River in present South Dakota. The general introduction by Gary E. Moulton discusses the history of the expedition, the journal-keeping methods of Lewis and Clark, and the editing and publishing history of the journals from the time of Lewis and Clark's return.