The Platteville Limestone is the Ordovician limestone formation in the sedimentary sequence characteristic of the upper Midwestern United States. It is characterized by its gray color, rough texture, and numerous fossils. Its type locality is Platteville, Wisconsin. It was heavily used in the early decades of the building of Minneapolis–Saint Paul and Faribault, Minnesota. In Illinois, the formation is elevated to group status and referred to as the Platteville Group.