During surveys in 2006, we documented 25 invasive exotic plant taxa in the restored prairie at Herbert Hoover National Historic Site. Sweetclover and reed canarygrass were widespread and abundant at Herbert Hoover National Historic Site. Sweetclover was very prevalent in the western half of the prairie, is established on at least 44 acres, and was found in 84% of search units. Reed canarygrass covered at least 4 acres and occupied 50% of the search units. Out of the 25 invasive exotic plants, 20 plants each occurred on less than one acre. In general, several invasive exotic plants are a major problem at Herbert Hoover National Historic Site, but successful control is possible for a large group of species. We suggest the development of a plan to manage sweetclover in order to maintain the composition of a relatively diverse prairie. The acreage estimates presented in the report may also be used to plan management activities leading to control of exotic plants and the accomplishment of GPRA goal IA1b.