Sled dog each year, but after the 1995 events, it was decided to hold them every two years, which facilitated the bidding process and enabled the host organization more time for preparation. Togo was the lead sled dog of Leonhard Seppala and his dog sled team in the 1925 serum run to Nome across central and northern Alaska. Balto was the lead dog of the sled dog team that carried the diphtheria serum on the last leg of the relay to Nome during the 1925 diphtheria epidemic. He was driven by musher Gunnar Kaasen, who worked for Leonhard Seppala. Seppala had also
Sled dog racing followed. For example, the ISDRA sanctioning rules specify that all hazards must be avoided, distances must be reported correctly, and the trail must be clearly described to the competitors. The racers have a duty to treat their dogs humanely, and performance-enhancing substances are strictly forbidden. Dryland Dog Sled Racing is a variant where competitors use a rig (3–4-wheeled cart with a locking brake and handle/steering wheel) or a scooter, a bicycle (Bikejoring), and on foot (Canicross) usually on packed dirt trails instead of a sled on snow. Another mode of dogsled racing is the "freight race," in which a specified