Balto was a Siberian Husky who delivered serum to Nome, Alaska in 1925.
In Darwin's Soldiers
Alexander "Balto" Nikolai was anthropomorphic, and a propellor plane pilot, in which he flew the serum to Nome. At least one film was made dramatizing his effort. Neville Ivers viewed part of this film in a hotel in September 2009. (Disruptive Selection)
In real life
Balto was merely the leader of a single dogsled team, and only carried the serum the final stretch of the ordeal. He was not anthropomorphic.