The Iditarod is a system of historic trails made famous by Alaska gold prospectors and their dog teams during the late 19th and early 20th century gold rush. Most of the trail is usable only during Alaska’s six-month winter when rivers and tundra are frozen. Each year the renowned 1,150-mile Iditarod Sled Dog Race is run along the trail from Anchorage to Nome. Other events include the 210-mile Iditasport race for skiers, mountain bikers, and snowshoers, and the Alaska Gold Rush Classic Snowmachine Race. A network of shelters is being installed by the Bureau of Land Management and the Iditarod Trail Committee.