This thesis deals with the flora of La Crosse County. It is primarily a revised account of the native and introduced vascular plants in the county. Situated in the ;;Drift-less Area;;, or unglaciated portion of the state, the area provides a variety of habitats, and a relatively large flora. This work is based on collections made in 1971 and 1972.During these years, collection areas across the county wererevisited from April to October. 3200 individual collectionshave been made and identified. This information was supplementedby viewing the collections made by other individuals that are deposited in the herbaria of the University of Wisconsin - La Crosse, University of Wisconsin - Madison, and the University of Iowa - Iowa City. 950 species representing 120 families have been confirm forthe county. The largest family represented is the Compositaewith 113 species and the largest genus is Carex with 70species.