Iditarod Trail Sled Dog Race differ by less than . The northern route first passes through Cripple, which is from Anchorage, and from Nome (ITC, "Northern"), making it the middlemost checkpoint. From Cripple, the route passes through Sulatna Crossing to Ruby, on the Yukon River. Ruby is another former gold-rush town which became an Athabaskan village. The southern route first passes through the ghost town of Iditarod, which is the alternate halfway mark, at from Anchorage, and from Nome (ITC, "Southern"). From Iditarod the route goes through the three neighboring Athabaskan villages of Shageluk, Anvik, Grayling, and then on to Eagle Island, Alaska. Ruby and
Iditarod Trail Sled Dog Race reveals the results of tests on the dogs. Each team is composed of twelve to sixteen dogs, and no more may be added during the race. At least five dogs must be on the towline when crossing the finish line in Nome. Mushers keep a veterinary diary on the trail and are required to have it signed by a veterinarian at each checkpoint. Dogs that become exhausted or injured may be carried in the sled's "basket" to the next "dog-drop" site, where they are transported by the volunteer Iditarod Air Force to the Hiland Mountain Correctional Center at Eagle River