Glaciers and their melting waters formed the prairie landscape and created soil from pulverized rock, with sand, silt, and clay particles forming a matrix that is nearly two thirds air pockets. The prairie’s life cycle continually aerates this soil as about one-third of the root mass dies each year, and soil bacteria decompose the dead roots, adding nutrients and creating space for water to infiltrate. Two-thirds of tallgrass prairie biomass lies underground, where an ounce of soil can hold 500 million bacteria, and a single cubic yard can support more than 250,000 spiders and insects as well as 13 million worms, alongside burrowing mammals, amphibians, birds, and extensive living roots. Tallgrass prairie protects soil from erosion, improves water quality, and provides wildlife habitat, making preservation and restoration important. In southern Minnesota, the loss of most native prairie to farming has left its deep, fertile soil as the most visible remnant; these soils came from deep water sediments of glacial Lake Agassiz deposited along the shores of the River Warren, now the Minnesota River. In the late 1800s and early 1900s, settlers farmed this land, and because prairie pothole wetlands were difficult to cultivate, farmers drained them with ditches and drain tile, reducing wetlands and harming pre-settlement wildlife populations. Butterfly Weed, a tallgrass prairie plant growing one to three feet high, has bright orange flowers and a deep woody tuberous taproot; European settlers used its root to treat chest inflammations and called it Pleurisy Root, while Native Americans used it for fiber, food, tea, and soap, though some parts were poisonous. Monarch butterflies are attracted to Butterfly Milkweed for its abundant nectar, and the plant’s toxins make them toxic or distasteful to birds and mammals when eaten by larvae. Tallgrass prairie, named for grasses that can reach six feet by late summer, is sometimes called an upside-down forest because much of its life is below ground. According to the National Park Service, 80 percent of its plants are grasses, with up to 60 species, while the other 20 percent are wildflowers, lichens, and liverworts. The prairie changes through the seasons, and fire, long a natural process and now also a restoration tool, helps maintain diversity by removing thatch and litter so new plants can grow. Some prairie roots extend more than 15 feet underground, helping control erosion, filter water, resist non-native plants, enrich topsoil, and withstand drought. Once stretching from Saskatchewan to Mexico and from east of the Mississippi River west to the Central Great Plains, tallgrass prairie covered one-third of Minnesota before European settlement, but only one percent of the state’s original tallgrass prairie remains today. The Prairie Passage Route runs through a Minnesota region that once held 18 million acres of tallgrass prairie and connects preserved and restored prairie sites as part of a six-state effort to protect, restore, and teach others about native prairie.