Crescent Lake National Wildlife Refuge in Nebraska protects 45,818 acres about 28 miles north of Oshkosh, including the nation’s largest protected continuous sand dunes. Formed through ancient glacial processes and exposed after the Pinedale glaciation, the landscape combines dry Sandhills ridges with wetlands created where aquifers feed lakes and ponds in low areas. Protected in 1931 to preserve habitat for migratory birds and other wildlife, it has become a notable birding area with about 200 recorded bird species and seasonal bald eagles. Its grasslands and waters also support diverse mammals, sport fishing, and quiet recreation, and it administers North Platte National Wildlife Refuge.