ABSTRACT
John C. Fremont, one of the most colourful and controversial figures in nineteenth-century US history, based his heroic reputation as an explorer of the American West on expeditions he led to the Rocky Mountains in 1842 and 1843–1844. The origins of Fremont's expeditions are more properly placed in the context of the Topographical Corps's long-term policy of systematic and professional exploration. While Fremont's exploits garnered public acclaim, the foundation for his success was laid by Secretary of War Joel R. Poinsett, Topographical Corps Chief Colonel John J. Abert, and the French scientist Joseph Nicollet, who had led previous expeditions and trained the young Fremont. The principle of scientific exploration and the drive to open the western territories operated on parallel lines for a time, to propel America's westward advance. Abert believed that Nicollet's scientific procedures would produce "the best map that has yet been published of the United States west of the Mississippi."
