Orchard Knob is a 2.5 ha National Military Park near downtown Chattanooga, Tennessee. This historic site protects a bubble of limestone glade and xeric limestone prairie habitat in an otherwise heavily developed, urban area. A floristic survey was conducted across two growing seasons, yielding 212 taxa across 152 genera and 58 families. Seventy-four non-native taxa were documented, about 35% of the total flora. Six rare, state-ranked species were documented: Baptisia aberrans, Clematis fremontii, Hypericum dolabriforme, Packera paupercula var. appalachiana, Symphyotrichum ericoides var. ericoides, and Viola egglestonii. An exploration of Civil War-era herbarium specimens and historical documents illuminated the historical flora of the site, and through the geolocation of herbarium specimens of select “indicator species,” the authors demonstrated that grassland habitats were once more abundant in the Chattanooga area.