The debate over the species status and geographic distribution of Rhinichthys atratulus and R. obtusus has persisted for decades. Morphological analyses have led to ambiguous results making field identifications possible in only some areas, further complicating the unclear and conflicting taxonomic histories of these species. In this study, we clear up some of these identification issues by analyzing two mitochondrial genes and nine microsatellite loci amplified from Blacknose Dace across the eastern half of North America. Our results show large genetic differences between R. atratulus and R. obtusus for both mitochondrial genes and microsatellites. We determine that R. atratulus inhabits streams east of the Appalachians from Nova Scotia to Virginia and the southern part of the eastern Great Lakes; R. obtusus inhabits the remaining regions west of the Appalachians to approximately Minnesota, eastern Nebraska, north into the Manitoba province and Mobile Bay drainage.