The early 20th century is often referred to as the Golden Age of Hollywood. During this period, movie studios like MGM, Paramount, and Warner Bros. dominated the industry, producing iconic films like "Casablanca," "The Wizard of Oz," and "Singin' in the Rain." The silver screen was the primary source of entertainment for millions of people, and movie stars like Greta Garbo, Clark Gable, and Humphrey Bogart became household names.