And here is the smoking gun. Elastigirl went into retirement November 13th, 1955. Between that and the cape accidents in ‘57 and ‘58 as mentioned in the No Capes montage, that puts the Super Ban around there. The “present day” action of the Incredibles film, which is 15 years later, is around 1970.
The Incredibles is a period superhero story like Watchmen or The New Frontier.