Hopalong Cassidy was the star of a series of novels set at the Bar 20 Ranch. They were written by Clarence E. Mulford over a span of 35 years, and had been the basis for a series of 66 movies between 1935 and 1948. The movies were adapted into a television show that originally ran at the same time as the radio program, and the licensing blitz that followed the show's popularity made "Hoppy" into one of the first multimedia sensations.