Valentine National Wildlife Refuge protects 19,131 acres of north-central Nebraska Sandhills prairie, wetlands, and dune country within the largest remaining area of tall and mid-grass prairie in the United States. Its landscape was shaped by the last ice age and the later stabilization of exposed sands as grasses took root, creating the distinctive prairie-and-dune environment. Numerous lakes, ponds, wetlands, and streams fed by seeps and springs support abundant wildlife. About 260 bird species have been recorded here, and roughly 150,000 birds pass through during spring and fall migration. Managed within the Fort Niobrara National Wildlife Refuge Complex, it was designated a National Natural Landmark in 1976.