Conservation concerns for imperiled crayfish faunas have recently increased among resource management agencies. In Maryland, major concerns include the introduction of nonnative crayfishes and their impacts on native species. This study documented the species distribution and conservation standing of native and nonnative crayfishes of western Maryland. Native species include Orconectes (Crockerinus) obscurus (Allegheny Crayfish), Cambarus (Jugicambarus) dubius (Upland Burrowing Crayfish), Cambarus (Cambarus) bartonii bartonii (Common Crayfish), and Cambarus (Cambarus) carinirostris (Rock Crawfish). Introduced species are Orconectes (Gremicambarus) virilis (Virile Crayfish), Procambarus (Ortmannicus) acutus (White River Crawfish), and Cambarus (Tubericambarus) thomai (Little Brown Mudbug). Nonnative species were found primarily in areas of high anthropogenic activity, with populations of O. virilis and P. acutus isolated to impoundments. The presence of C. thomai in Maryland was first documented through this study, and represents one of the first situations globally of a primary burrowing crayfish outside of its native range. Major conservation threats to the native crayfish fauna of western Maryland include nonnative crayfishes, land development, and land-use practices.