Happy Birthday: The Hays Code
On March 31, 1930, the Movie Producers and Distributors Association (the MPPDA) first instituted its Production Code, also known as "The Hays Code," because lawyer Will H. Hays headed the association.
The code prohibited filmmakers from producing anything that did not show “correct standards of life, subject only to the requirements of drama and entertainment.” This included any and all nudity, depiction of illegal drug use, offensive words, and ridicule of religion or marriage. On July 1, 1934, the Production Code Administration was established and every film was required to have a certificate of approval from them before it could be released.
The MPPDA became the Motion Picture Association of America (the MPAA) and continued to administer the Code until 1967, when MGM released the film Blowup despite being refused approval. The MPAA then worked on a rating system instead, and put it into effect on November 1, 1968. A modified version of that rating system is still used today.