In western Iowa, from Sioux City south to Hamburg, the Missouri River flood plain is bordered by a series of abrupt loess bluffs. Because of the wide variability in exposure, because of the characteristic wind-deposited loess and because of the accessability to river migration routes, the bluffs possess a diverse, albeit characteristic flora. Investigations of localized or specialized ecological niches frequently yield not only floristic data but insight into historical development and migration movements of both individual species and floristic units. For instance, McLaughlin (1932) in his study of the sand barren flora of northwest Wisconsin was able to show possible migrational routes of the Atlantic coastal plain flora into Wisconsin. Although certain aspects of the bluff flora have previously been described (Pammel, 1902; Shimek, 1909; Conard, 1952), no inclusive botanical survey of the area has been made. The present study, undertaken to fill such a need, is designed not only to provide a reasonably complete floristic survey of the bluff flora, but also to consider the components of the flora from an ecological and geographical standpoint.