The flora at Riverdale Park was sampled during the 2021 growing season, April through October, to create an inventory of the native and nonnative vascular plant species. One hundred ninety species in 151 genera in 85 families were identified. Maples, Acer spp., and oaks, Quercus spp., were the most diverse genera in the flora with six species, while Rubus was represented by four species. Seventy-six taxa, 40% of the flora, were not native to the region. Many nonnative vascular plant species may be relicts of the past land use history, as Riverdale Park is situated on old estates created in the 1800s. The high percentage of nonnative taxa in the Riverdale Park study is related to the urban environment and past land use history.