For centuries, sled dogs pulled the people of northern climates over otherwise impassable distances of snow and ice, guiding them home through trackless wilderness. These burly, strong dogs were the lifeblood of the northern winter world. Today, from races like the famed Iditarod and the John Beargrease Sled Dog Marathon to sled dog tours, people from all climates are rediscovering the joy of this dog-powered sport.