The program was an adventure series about Sergeant William Preston of the North-West Mounted Police and his lead sled dog, Yukon King, as they fought evildoers in the Northern wilderness during the Gold Rush of the 1890s. Preston, according to radio historian Jim Harmon, first joined theMounties to capture his father's killer, and when he was successful he was promoted to sergeant. Preston worked under the command of Inspector Conrad, and in the early years was often assisted by a French-Canadian guide named Pierre.
Preston's staunchest ally, who was arguably the true star of the show and indeed often did more work than he did, was the brave Alaskan husky, Yukon King. Typical plots involved the pair helping injured trappers, tracking down smugglers, or saving cabin dwellers from wolverines. Sergeant Preston's faithful steed was Rex, used primarily in the summer months, but generally Yukon King and his dog team were the key mode of transportation (as signaled by Preston's cry of "On, King! On, you huskies!)."
There is some confusion regarding King's actual breed. The writers seemed to use malamute and husky interchangeably. At least once, Preston answered "malamute" to the question from another character. In one radio episode Preston indicates King's mother had been a wolf, which would make him a wolfdog. In the early radio shows, the cry of "On, you huskies!" would alternate with "On, you malamutes" from show to show.
The theme music was Emil von Reznicek's overture to Donna Diana, a now long-forgotten opera, though the overture remains a concert staple to this day. The show's episodes ended with the official pronouncement, Well, King, this case is closed. [Source: Wikipedia]