Marais des Cygnes National Wildlife Refuge is a 7,500-acre protected area in eastern Kansas along the Marais des Cygnes River, established in 1992 to preserve one of the northwesternmost remaining examples of bottomland hardwood forest in the United States and the largest contiguous tract of that habitat in Kansas. Its landscape also includes upland oak-hickory forest, tallgrass prairie, wetlands, and riverine habitat, creating unusual ecological diversity in one place. Because bottomland hardwood forest and tallgrass prairie have largely disappeared elsewhere, the refuge is especially important for sustaining threatened species and a rich variety of wildlife, including many warblers, mussels, mammals, fish, amphibians, and birds.