Film theory

Films blossomed in the 1920's , Most of the US films production at the start ocurred near Hollywood on the West coast
although some films were still being made in New Jersey and in Astoria on Long Island (Paramount). By the mid-20s, movies were big business (with a capital investment totaling over $2 billion) with some theatres offering double features. By the end of the decade, there were 20 Hollywood studios, and the demand for films was greater than ever. Most people are unaware that the greatest output of feature films in the US occurred in the 1920s and 1930s (averaging about 800 film releases in a year) - nowadays, it is remarkable when production exceeds 500 films in a year.

Throughout most of the decade, silent films were the predominant product of the film industry. But the films were becoming bigger costlier, and more polished. They were being manufactured, assembly-line style, in Hollywood's 'entertainment factories,in which production was broken down and organized into its various components (writing, costuming, makeup, directing, etc.).

Even the earliest films were organized into genres or types, with instantly-recognizable storylines, settings, costumes, and characters. The first feature documentary or non-fictional narrative film.

Taken from: http://www.filmsite.org/20sintro.html
http://en.wikipedia.org/wiki/History_of_film