At the May, 1929 Academy Awards ceremony, Wings became the first film ever to win a Best Picture Oscar 

Prior to 1930, when this film was made, there were no official standards for what could and could not be shown in theaters. It was left to theater owners to gauge the standards of their own communities. The industry's self-policing Hays Code was enacted in 1930, but it had no teeth for enforcement, so sporadic nudity continued to pop up in films until a day that will live in infamy, July 1, 1934. While that date is not as black a mark on American history as Dec 7, 1941 or Sept 11, 2001, it certainly had a substantial and almost entirely negative impact on American culture for more than three decades.

The voluntary compliance (wink-wink!) era of 1930-34 came to an end when the American Catholic Church announced the creation of its Legion of Decency, which encouraged the production of moral films by promptly condemning any film with an immoral message or content. The Legion's activism hit the film industry in two vulnerable areas. First, the Legion's threats to boycott objectionable films went directly for the purse strings. Second, the Legion threatened to lobby the federal government for official censorship. The industry's leaders saw the handwriting on that wall. They knew the Legion could exert a powerful influence over politicians, and they realized that self-censorship was a far more attractive alternative to draconian government interference, so they were forced to create a formal procedure to administer the existing code. All films released after July 1, 1934, had to get script approval before production could begin, and each film was later required to obtain a "seal of approval." Failure to comply resulted in a $25,000 fine for the studio, and a distribution ban upon the non-compliant film.

Those rules basically kept nudity out of American movies for approximately the next thirty years. The Legion did not begin to lose its grip on Hollywood until 1964 when Sidney Lumet's acclaimed The Pawnbroker managed get an Oscar nomination while sneaking fairly substantial nudity into arthouse theaters, despite a "condemned" rating from the Legion.

So, wear your black armband for American films from 1934 to 1964, three decades almost completely devoid of nudity in mainstream productions.

Moreover, a cultural shift did not happen overnight. The Pawnbroker stuck a foot in the door to freedom, but moral conservatives continued to resist opening that portal. Despite a rapidly liberalizing climate in the mid sixties, it was not until 1968 that the Production Code was finally and officially replaced with the first version of the current rating system.