Big Bay Sand Spit and Bog is located on an island in Lake Superior and features a long, curving baymouth bar behind which lies a lagoon, an extensive quaking sphagnum-sedge bog, and older sand ridges. The youngest bar is marked by four zones: 1) wet sand beach less than 20 feet wide; 2) dry beach stabilized by several species of beach grasses; 3) rear beach or heath zone sloping away from the beach sand, sparsely wooded with red and white pines in barrens-like openings covered with lichens, bearberry, low juniper, false heather, blueberry, and huckleberry; and 4) tall shrub zone bordering the lagoon edge of the sand spit. Total beach acreage is 34 acres. Vegetation west of the sand spit consists of submerged aquatics in the shallow water and bog shrubs on the many small islands as it grades into sphagnum-sedge bog. The floating bog contains one of the richest bog floras in the Lake Superior region. Just east of the old ridge is a conifer swamp of white cedar, black and white spruces, and tamarack. The old ridge is second-growth timber. Two state-threatened plant species are found on the site: linear-leaved sundew (Drosera linearis) and coast sedge (Carex exilis). An extensive "cordwalk" allows visitors to traverse the baymouth bar without disturbing the sensitive vegetation. Big Bay Sand Spit and Bog is owned by the DNR and was designated a State Natural Area in 1980.