Lost Creek Bog features a Lake Superior estuarine system at the drowned mouths of three small creeks (Lost Creek 1, 2, and 3) where they empty into Siskiwit Bay. A coastal barrier sand spit forested with spruce and pine separates the wetlands from the lake. Shore fen, grading to open sedge bog, shrub swamp, and northern wet forest dominated by tamarack are the major communities in the natural area. The fen is well developed on the west and north sides of the lagoon, with a mat composed of woolly sedge, bogbean, sweet gale, and cotton grass. Boggy areas are dominated by Sphagnum mosses, sedges, leather-leaf and other ericaceous shrubs. Lost Creek 1 and 2 are flat, shallow, cold water streams with sandy bottoms that sustain a small brook trout population. Lost Creek 3 is a warm water drainage stream supporting minnows. The emergent marsh at their confluence harbors the largest known Wisconsin population of the state-endangered lake cress (Armoracia lacustris). Flora of the marsh is composed of lake sedge, water arum, marsh cinquefoil, and cat-tail. Bur-reed, water milfoil, yellow water-lily, common bladderwort, and pondweeds are among the submergent and floating-leaved species in the marsh. Several rare plants and animals have been recorded in the natural area, including dragon's-mouth orchid (Arethusa bulbosa), livid sedge (Carex livida), Hooker’s orchid (Platanthera hookeri), bog fritillary butterfly (Boloria eunomia), and bog copper butterfly (Lycaena epixanthe). Uncommon nesting birds recorded here are yellow-bellied flycatcher, evening grosbeak and merlin. Migratory waterfowl and other water birds make extensive use the site. Lost Creek Bog is owned by the DNR and was designated a State Natural Area in 1993.