two of the world's most iconic superheroes and recognizable fictional characters were introduced in comic books; Superman first appeared in 1938, and Batman in 1939. The pulp fiction magazines begin to feature distinctive, gritty adventure heroes that combine elements of hard-boiled detective fiction and the fantastic adventures of earlier pulp novels. Two particularly noteworthy characters introduced during this time are Doc Savage and The Shadow, who would later influence the creation of characters such as Superman and Batman. Popular comic strips which began in the 1930s include Captain Easy by Roy Crane, Alley Oop by V. T. Hamlin, Prince Valiant by Hal Foster, and Flash Gordon by Alex Raymond. David Alfaro Siqueiros paints the controversial mural América Tropical (full name: América Tropical: Oprimida y Destrozada por los Imperialismos, or Tropical America: Oppressed and Destroyed by Imperialism) (1932) at Olvera Street in Los Angeles, California. Best-selling books The best-selling books of every year in the United States were as follows: 1930: Cimarron by Edna Ferber 1931: The Good Earth by Pearl S. Buck 1932: The Good Earth by Pearl S. Buck 1933: Anthony Adverse by Hervey Allen 1934: Anthony Adverse by Hervey Allen 1935: Green Light by Lloyd C. Douglas 1936: Gone with the Wind by Margaret Mitchell 1937: Gone with the Wind by Margaret Mitchell 1938: The Yearling by Marjorie Kinnan Rawlings 1939: The Grapes of Wrath by John Steinbeck Film Charlie Chaplin's groundbreaking classic, "City Lights", was released in 1931. Charlie Chaplin's last film featuring his signature character, "The Tramp", was subsequently released in 1936. Walt Disney's Snow White and the Seven Dwarfs was released in 1937. The Little Princess was released in 1939. The Wizard of Oz was released in 1939. In the art of filmmaking, the Golden Age of Hollywood enters a new era after the advent of talking pictures ("talkies") in 1927 and full-color films in 1930: more than 50 classic films were made in the 1930s; most notable were Gone With The Wind and The Wizard of Oz. The new soundtrack and photographic technologies prompted many films to be made or re-made, such as the 1934 version of Cleopatra, using lush art deco sets, which won an Academy Award (see films 1930–1939 in Academy Award for Best Cinematography). Universal Pictures begins producing its distinctive series of horror films, which came to be known as the Universal Monsters, featuring what would become iconic representations of literary