High Quality Content by WIKIPEDIA articles! During the 1925 serum run to Nome, also known as the "Great Race of Mercy", 20 mushers and about 150 sled dogs relayed diphtheria antitoxin 674 miles (1,085 km) by dog sled across the U.S. territory of Alaska in five and a half days, saving the small city of Nome and the surrounding communities from an incipient epidemic.