Often referred to as the "Kusko 300", or "K-300", the race has been held every January since 1980 (except 2021 which was held in February), and commemorates an early mail route that once tied the settlements along the river to the outside world. Top mushers and hundreds of sled dogs participate in the race for a purse of $160,000, the largest offered by any 300-mile (480 km) sled dog race.
The race is renowned for its often difficult weather and trail conditions. The inaugural race saw a fierce blizzard with dangerously low windchills for the first half of the race, followed by a freak thaw and rain for the latter half. Three separate K-300s (1991, 1999, 2008) earned the nickname "Kusko-Swim", due to strong winds, rain, and deep overflow on top of the river ice.
2021 saw the race rescheduled for mid-February, avoiding Super Bowl LV.
