Clarence E. Mulford created Hopalong Cassidy, a fictitious cowboy featured in various books, movies and a television show. Mulford created the character in 1904. The first Hopalong Cassidy novel is "Bar-20," which Mulford wrote in 1906.
Beginning in 1935, various Hollywood producers made 66 films about Hopalong Cassidy. Only a few of the movies were based upon Mulford's books. William Boyd, who played Cassidy, purchased the rights to the character from Mulford in 1944. In 1949 he pitched an idea for a television show based on Cassidy to NBC. It was the first network Western television show. In addition to books, films and a television program, a radio show and comic books were based on the character.