The MPAA decided at the time that if anyone was going to regulate the content of the films being put out in the United States that they, not the government, would be the ones to do it.

The code first started out with the nickname the Hays Code, named after the man who invented it, but it later had to be revised to include a SMA or Suggested For Mature Audiences rating, which was intended to note that a film contained what most people would see as objectionable content.

Even though this first rating was introduced, which films it would apply to was not standardized and those film production companies that did not belong to the MPAA were not subject to this rating system.

From 1968 to 1970, the rating system only consisted of four different ratings: G, M, R, and X, with increasing levels of violence, sex, or profanity. This rating was changed to GP or General Patronage and then from GP to PG Parental Guidance in March of 1970.

The rating of PG-13 came around in the mid 1980's, since there were a lot of films that were right on the line between the PG and the R rating. The PG-13 rating was created to fill in this gap.

The NC-17 rating came into existence on September 27th, 1990 and this rating replaced the X rating that had been used almost since the beginning of the ratings system. The X rating had become too synonymous with pornography and this was never intended.

The problem with NC-17 ratings for producers, however, is the fact that some movie store chains will not carry titles that carry its stamp. This has caused film studios to recently protest the NC-17 rating for films, stating that it makes their films almost worthless for widespread release, since many movie rental chains will not carry titles that are rated NC-17.

Recently the rating that has been coming under some fire is the R rating. It has a similar problem today that the PG and R ratings had that lead to the creation of the PG-13 rating back in the mid 1980's in the sense that there are a large number of films that are considered to be just on the border between R and NC-17. Many parents believe that the R rating is a bit too broad and would like to see the rating split up into 2 groups: R and Hard R.