An inventory of the bryophytes of Loud Thunder Forest Preserve (Rock Island, IL) was conducted in order to improve the knowledge of the bryoflora of the county. In total, 38 species were identified, adding 19 new taxa to the county checklist (53 mosses and 9 liverworts). Most of the existing collections of the bryoflora in the area were made more than a century ago, and since the new additions are common species this suggests that moss and liverwort diversity in Rock Island County is still underexplored.