Challenge of the Yukon was a radio series that began on Detroit's station WXYZ (as had The Lone Ranger and The Green Hornet), and an example of a Northern genre story. The series was first heard on February 3, 1938. The title changed from Challenge of the Yukon to Sergeant Preston of the Yukon in November 1951, and remained under that name through the end of the series and into television. 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 the Mounties 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.