Not to discourage any further answers, but these older posts are worth a read:

Is Plato's Critias the only historical text to mention Atlantis?

Did Greeks of Plato's time (or later) think that Atlantis had actually existed in the past?

By /u/XenophontheAthenian

This answer by /u/Iphikrates also touches on the origins of the Atlantis fable.