Herein we clarify the taxonomy of Fluminicola coloradensis Morrison (1940), which was described for populations in the Green River and Bonneville basins but has also been treated as restricted to the former watershed and conspecific with (currently unassigned) Snake River basin populations of Fluminicola hindsi sensu Taylor (1966). Bayesian analyses of DNA sequences from 2 mitochondrial genes congruently resolved F. coloradensis and Snake River basin populations of F. hindsi sensu Taylor as a strongly supported, shallowly structured clade. Haplotypes were extensively shared by Bonneville, Snake River and Green River populations; AMOVA did not detect significant variation among basins for either gene. Morphological variation was minor. Based on these results, we assign the Snake River basin populations to F. coloradensis. We attribute the limited differentiation of widely ranging F. coloradensis to its well-integrated habitats and to dispersal mediated by geologically recent drainage transfers. The broadly disjunct population in the Owyhee River drainage may be a product of translocation, as evidenced by detection of only the most common haplotypes in these snails. Our finding that F. coloradensis is more widely distributed than previously thought suggests that it may not require conservation attention rangewide, although some geographic subunits may be at risk.