The Substitution

Challenge of the Yukon is an American radio adventure series that began on Detroit's WXYZ and is an example of a Northern genre story. The series was first heard on January 3, 1939. The title changed from Challenge of the Yukon to Sergeant Preston of the Yukon in September 1950, and that title was retained through the end of the series and into a television adaptation.

Wikipedia. CC BY-SA 4.0. Updated Jul 26, 2026.

“The Substitution.” Challenge of the Yukon. Radio broadcast, February 11, 1947.