While travelling to and from work, the senior author noted a vigorous bramble covering about a 20-meter section of hillside along a road bordering the North Central Regional Plant Introduction Station farm, southwest of Ames, Iowa. Upon closer examination, the bramble seemed to be significantly different from those species described in floras of surrounding states (Great Plains Flora Association 1986, Mohlenbrock 1986, Steyermark 1963). This plant was identified as Rubus parvifolius L. ( = R. triphy!lus Thunb., non R. parvifolius Walter), the trailing raspberry, using Rehder's (1940) key. The senior author initially suspected that this species had merely been persisting near the Plant Introduction Station after cultivation, but then he noticed the same bramble in other locations around Ames, where the plant was naturally reproducing and clearly not under cultivation. This species' vigorous growth (at one site it covers over 1000 square meters of thin woodland understory) and its production of fruits attractive to birds suggest that the plant is now well established and should be considered a member of the local flora. The discovery of R. parvifolius in Iowa, along with its absence from nearly all North American floristic manuals, prompted this work.