The Grand River Museum in Lemmon has a large amount of actual dinosaur fossils from the northwestern part of South Dakota. Our exhibits feature Ranching, Dinosaur Fossils, Native American History, Hugh Glass and more. Stop in for a quick visit, or longer. Be sure to check out the gift shop. The museum is open May through September. Hours are 9 a.m.-5:30 p.m., Monday through Saturday, and 12-5 p.m., Sunday. Admission is free, however donations are accepted.