The Oscars red carpet was not always about designer gowns but rather, it was where Hollywood's hottest looks were created by the all-powerful studio costume designers. The looks created were intended to maintain the mystique and supernatural-ness of the actors.
As Edith Head prophetically stated in 1970:
“You’re going to see at the Academy Awards the world’s greatest fashion show… you’re going to have fashions from every great designer all over the world modeled by the most beautiful women in the world, the Hollywood stars.”
This article from Vogue takes a look at the Oscars red carpet over the last 70 years.