ABSTRACT Much of western Sainte (Ste.) Genevieve County, Missouri, is underlain by parts of the LaMotte sandstone formation. The geological properties of this bedrock have led to the formation of canyons and cliffs, which harbor ‘‘glacial relicts’’ and other regionally rare, restricted plant species. A partial survey of the flora at Horton Farm Conservation Area (HFCA) in Ste. Genevieve County was performed from June 2012 to July 2014 to provide local conservation officials with relevant data to make informed management decisions. Four specific areas of interest were selected: a cliff complex near Rough Creek, a small acid seep, a glade/woodland complex, and the riparian corridor along Jonca Creek. A total of 214 vascular plant species was collected from HFCA: 23 from the acid seep area, 120 from Jonca Creek, 48 from the glade/woodland, and 77 from the cliff area. Included were 5 species of conservation concern, and 16 county records were documented. A checklist of the collected species is included, and a new combination is published—Aureolaria flava (L.) Farw. var. calycosa (Mack. & Bush) A.P. Braun.