Hopalong Cassidy's Rustler Round-Up; Or, Bar-20 is a Western novel by Clarence Edward Mulford. It tells the story of Hopalong Cassidy, a cowboy who helps to round up a gang of rustlers who are stealing cattle from the Bar-20 ranch. The book is set in the American West in the late 19th century. It features a cast of memorable characters, including Hopalong Cassidy, a skilled cowboy and a capable gunfighter; Red Connors, Hopalong's best friend; and...