Kennesaw Mountain National Battlefield Park, Cobb County, GA, is administered by the National Park Service, United States Department of the Interior, and comprises 1183 ha (2923 acres) including three significant Civil War battleground sites of the Atlanta Campaign of 1864. A floristic survey was conducted to provide Park Service personnel with a vouchered plant species checklist, supplemented with salient information such as relative abundance, locality data, and general community type. Twelve collecting trips conducted in 2006 yielded 538 species and two varieties of vascular plants. The six largest families were Asteraceae (73 spp.), Poaceae (69 spp.), Fabaceae (39 spp.), Rosaceae (21 spp.), Cyperaceae (19 spp.), and Lamiaceae (14 spp.). According to state rankings, six rare plant species occur within the study area, including Asclepias purpurascens (rare) and Thaspium pinnatifidum (endangered). Twenty-three percent of the non-cultivated flora is nonnative. Alliaria petiolata, a serious invasive exotic, was vouchered for the first time in Georgia. Herein, we provide a vouchered checklist of vascular plants and a map and descriptions of the general plant communities. Additionally, an earlier unvouchered list prepared by Park Service personnel is included with updated nomenclature and taxonomy.