In the winter of 1925, there was a diphtheria epidemic among Inuit in the Nome area. Blizzard conditions made delivery of a life-saving serum by airplane from Anchorage impossible. A serum run to Nome by dog sled teams delivered the serum. The sled driver of the final leg of the relay was the Norwegian-born Gunnar Kaasen; his lead sled dog was Balto. The annual Iditarod Trail Sled Dog Race commemorates this historic event.