Tulotoma magnifica (Conrad, 1834) is an enlarged operculate gastropod, formerly found throughout the Coosa River system in Alabama, USA whose range has been severely reduced and is now listed as endangered. We found its current range in 4 of 6 tributaries to be greater than in previous surveys. Neither abundance nor size of T. magnifica was consistently related to five habitat factors that we measured (rock surface area, rock height, water depth, current speed, abundance of other snail species), explaining less than 12–18% of the variation. While T. magnifica consistently used larger and taller rocks, there was no consistent difference in water depth, current speed, and abundance of other snail species between rocks with versus without T. magnifica. Isozyme variation of T. magnifica was greatest in the main channel Coosa River population; some Coosa River alleles were not detected elsewhere. Populations were at Hardy-Weinberg equilibrium at all but two of 17 loci examined, indicating random mating, no selection, no migration, and no mutation (except at those two loci). Genetic similarity (S) among populations ranged from 0.88–0.97; the smaller values are at a level that potentially suggests different subspecies, due primarily to a near fixed difference in allele frequency at the GPI locus. The distribution of T. magnifica within areas where it has been found is greater than thought based on recent surveys. In addition, there exists suitable unoccupied habitat at most sites. We suggest that some of these areas represent locations that could be considered for future efforts at recolonization, should that fit within the species recovery plan.