An inventory of vascular plants was conducted in Steele Creek Park in Sullivan County, Tennessee from March 2013 to September 2014. The park covers an area of 892 ha and lies within the Ridge and Valley Province. The inventory of vascular plants documented 547 species of 323 genera and 101 families. Two hundred sixteen taxa were newly reported for Sullivan County. Tennessee Special Concern Species included Cardamine rotundifolia, Castanea dentata, Lonicera dioica, Allium tricoccum, Cypripedium acaule, and Panax quinquefolius. A single species, Juglans cinerea L., is considered a Tennessee Threatened Species. Vegetation patterns were studied quantitatively by installing 10 study plots within forest canopy gaps and a comparable set of 10 in areas with intact canopy. Plots within a canopy gap recorded more vascular plant diversity when compared to plots of intact canopy when unshared species were considered. Steele Creek Park provides a botanically rich area for future studies.