Oakfield Ledge is one of the most significant exposures of the Niagara Escarpment in Wisconsin, a 650-mile long ridge that runs north from Waukesha County, forms the spine of the Door peninsula, then arcs east through Ontario, and ends at Niagara Falls in New York. Located along the Horicon Marsh, the hard, erosion resistant Niagara dolomite walls form a series of prominent rock cliffs 40' high - what locals call "the ledge." Deep crevices have formed along fractures in the bedrock. The vegetation of the shaded cliff and boulder strewn steep slope is the most undisturbed and consists of basswood, sugar maple, slippery elm, rock elm, mountain maple, and shagbark hickory. Groundcover includes extensive patches of Canada yew and the shaded cliffs provide habitat for walking, cliff brake, and fragile ferns. Spring seeps provide a moist forest floor habitat for interrupted fern, wild sarsaparilla, and pale-flowered leafcup and small creeks with mud bottoms contain great blue lobelia and swamp saxifrage. A diverse snail fauna inhabits the base of the ledge. Oakfield Ledge is owned by the DNR and was designated a State Natural Area in 1983.