Freshwater mollusks are widely used as bioindicators in the development of water quality criteria, including those for ammonia. EPA’s most recent freshwater ammonia criteria guidelines incorporate prosobranch gastropods. Freshwater mussels are commonly surveyed in Missouri, however, comparable data for gastropods are limited. In 2020, a volunteer-based statewide survey of freshwater snails was initiated to generate baseline occurrence data to support the development of ammonia water quality criteria for Missouri. Specimens were collected by volunteers participating in a statewide participatory science program and submitted for identification and data analysis. We will give an overview of the data collected over the last 5 years and discuss the future of this project. This project documents the presence of multiple freshwater snail taxa across diverse habitat types and geographic regions, represents the first coordinated volunteer-based effort to survey freshwater snails in Missouri, and contributes to a growing statewide dataset on gastropod occurrences.