The mid-Atlantic accent, which is now obsolete, wasn’t region-specific, and it was acquired, not natural. It was distinctive in that it was, as the name implies, a hybrid of American and British accents.
Although the idea that it was developed to ensure that speakers could be understood broadcasters through available technology of the early 20th Century is one theory about its origins, more evidence suggests that it was developed and learned as a signifier of class, having been taught at elite boarding schools in the American Northeast before proliferating in Hollywood cinema.
A 2016 investigation by Atlas Obscura, an online travel company and magazine, traced the accent’s origins to classism and elitism, not technology-driven necessity: