The 12,000-acre St. Louis River Estuary is the largest freshwater estuary in North America and is the headwaters of the Great Lakes. It is also the largest U.S. tributary of Lake Superior, which holds 10% of Earth’s fresh surface water. Water flow and the natural movement of sediments in estuaries combine to provide unique, productive, shallow water habitats. The combination of ecosystems within the Estuary — estuarine wetland and aquatic habitats, backwater bays, islands, baymouth bar complex, and uplands supporting large areas of forest vegetation — is very unusual in the Great Lakes, and around the world.

The Estuary is intimately tied to over two million acres of land forming the St. Louis River watershed, which provides nutrients and sediments as it replenishes water. The ecosystem hosts exceptional biodiversity: animals from mayflies to otters, plants from wild rice to white pine, fungi from earthstars to shaggy manes, and microorganisms from green algae to bacterial decomposers.

Over one million acres of wetlands represent a significant source of productivity for the entire Lake Superior ecosystem, and more than 10,000 acres of protected waters serve as the primary nursery for the more than 45 species native to Superior’s western end, such as lake sturgeon, muskellunge, walleye, and smallmouth bass. The Estuary serves as migrant corridor or breeding habitat for 238 bird species, including three species of loons, common terns (threatened), piping plovers (endangered), and peregrine falcons (formerly extirpated, now species of special concern).