Hopalong Cassidy was a radio western program that depicted the adventures of Hopalong Cassidy, a character created by writer Clarence E. Mulford. Set at the Bar 20 Ranch, the show featured stories based on the popular movies and television series, which were themselves inspired by Mulford's series of novels. The adventures highlighted the unique personality, mannerisms, and unusual exploits of the main protagonist, who was portrayed as a civilized knight of the range and a man of morals. William Boyd voiced Hopalong Cassidy, while Andy Clyde co-starred as California Carson, his trusty sidekick from many of the later films.

The radio show aired from 1948 to 1952, with its initial broadcasts on the Mutual network before ending on CBS on December 27, 1952. The program gained popularity as it simultaneously ran alongside the television adaptation, the first of its kind on KTLA in Los Angeles. Hopalong Cassidy became one of the first multimedia sensations, with both the radio and television versions benefiting from the popularity of the original character and movies. The show featured a total of 66 movies across 35 years and was produced by Walter and Shirley White, Charles Henry, and directed by Ted Bliss. The show's success served as a platform for advertisers and sponsors who capitalized on the established following that the character had developed.

Sources: archive.org, wikipedia.org