This checklist documents liverworts found in the Comanche National Grassland of Colorado with the intention of enriching our understanding of bryophyte biodiversity in Colorado as well as the high plains region. The study area sits beside the Purgatoire Watershed in southeastern Colorado, which lies between the Chihuahuan Desert and the Rocky Mountains ecosystems. Specimens from the grasslands were collected, reviewed and accessioned. These records add to our understanding of bryophyte biodiversity in Colorado and facilitate comparisons of species distributions through time. Eight species of liverworts were found: Aneura pinguis (Aneuraceae), Mannia californica, Mannia fragrans, Plagiochasma rupestre, P. wrightii, Reboulia hemisphaerica (Aytoniaceae), Frullania riparia (Frullaniaceae), and Riccia atromarginata (Ricciaceae). Mannia californica and Riccia atromarginata are newly documented for Colorado. The distributions, morphological characters and phylogenetic affinities of both these species are discussed.