The book describes the Government-backed expedition to explore the newly acquired Louisiana Purchase undertaken from 1804 to 1806 by ascending the Missouri to its source, crossing the Rocky Mountains, and reaching the Pacific Ocean. In total, the expedition covered some eight thousand miles in slightly more than twenty-eight months. Lewis and Clark brought back the first reliable information about much of the area they traversed, made contact with the Indian inhabitants as a prelude to the expansion of the fur trade, and advanced by a quantum leap the geographical knowledge of the continent.
