The Hollywood Studio System emerged in the 1920s as the dominant film production model in the US. It involved the major studios known as the "Big Five" vertically integrating all aspects of filmmaking from production to distribution and exhibition. Films were mass produced using an assembly line approach with specialized roles and repetitive tasks to efficiently turn out movies. The system ensured a constant flow of films across genres and styles through its contracted stars, directors, crews and soundstage facilities. It dominated Hollywood filmmaking from the 1930s to 1950s before declining due to challenges from independent producers and new technologies.