This is an investigation of the historical and current distribution of freshwater snails of Nebraska and South Dakota. This study ranges from historical surveys conducted in the late 1800’s to the early 1900’s, to recent survey results from over 260 water bodies throughout eight EPA Level III ecoregions. Species composition is compared among regions. Some species were observed in many water bodies across both states while other were comparatively rare: Common species include the left-handed pondsnail, Physa gyrina, and the large planorbid Helisoma trivolvis, while rare species include the freshwater limpet, Ferrissia rivularis, and the Prairie Lymneid, Lymnaea bulimoides. Reasons for their distribution is explored and I assign a conservation status to each species based on incidence, historical presence, and geographic distribution. Three species are imperiled, one species is critically imperiled, and at least seven species, observed only in historic studies, may be extirpated.