Demacentor andersoni (Ixodidae) is one of the most important disease vectors in Montana. Ticks transmit more animal disease agents of all bloodsucking arthropods. Ticks are the second most important vector in public health and the most important in veterinary medicine. Dermacentor andersoni is the vector of Rocky Mountain spotted fever, Colorado tick fever, tularemia, Bovine anaplasmosis, and Powassan encephalitis. According to Tabachnick and Black (1995), “population genetic studies of arthropod disease vectors provide opportunities for understanding their role in arthropod-borne disease, and for developing more effective control strategies.” This study will use inter-simple sequence repeats (ISSRs) to assess genetic variation within and among populations. Using an analysis of molecular variance (AMOVA) and population pairwise fixation index (FST) to determine statistical differences in ISSR banding patterns. Banding patterns will then be used along with geographic information systems (GIS) to determine if there are any significant barriers to gene flow and where these barriers arise.