abstract: This study was designed to produce a comprehensive flora of Usery Mountain Regional Park and Pass Mountain of the Tonto National Forest. A total of 168 vascular plant species representing 46 families and 127 genera were collected or documented at this study area. Sixteen species were not native to the flora of Arizona and represent 9.5% of the flora. Nevertheless, the study area does not appear to be significantly damaged or degraded in spite of its historical and current land use. The location and types of invasive species recorded in this study will assist with implementing preventative measures to prevent further spreading of certain species. The complete list of all vascular species recorded in this study will provide a valuable tool for land management decisions and future restoration projects that may occur at this area or similar sites and invasive species control. The distribution of the saguaro (Carnegiea gigantea) population on Pass Mountain was documented through the measurement of saguaros by random sampling. ArcGIS was used to generate 50 random points for sampling the saguaro population. Analysis to determine saguaro habitat preferences based on the parameters of aspect, slope and elevation was conducted through ArcGIS. The saguaro population of Pass Mountain significantly favored the southern aspects with the highest concentration occurring in the southwest aspects at an average density of 42.66 saguaros per hectare. The large numbers of saguaros recorded in the younger size classes suggests a growing populations. / Dissertation/Thesis / M.S. Applied Biological Sciences 2011