Before watching the movie:
When I was very young, I had a book about Balto, the heroic sled dog that saved the diptheria inoculation run from Anchorage to Nome that the Iditarod race commemorates. I don’t really recall why Balto was particularly celebrated as the hero of the relay, and it looks like this movie will not be very concerned with that.
The summary seems to indicate that the main conflict comes from how the other characters treat Balto because he is a wolfdog, but that’s not a detail I recall from the history. Apparently, the real Balto was a purebred husky, so I guess the movie’s main concern was a clumsy message about race.