For those unfamiliar with My Hero Academia, it's set in a world much like our own, except a couple of generations ago, humans started developing super-powers, or "Quirks". By the present day, about 80% of the human race has a Quirk of one kind, or another, and, as in Top 10, a person has to be trained and licensed in order to fight crime.
I just read volume three of a spin-off series, My Hero Academia: Vigilantes. The series has made American comics references before - two supporting characters are essentially Cyclops and Wolverine as Japanese street punks.
In this volume, the protagonist, a young college student, is being tutored in hero history, and it comes out that the first place to license heroes was Rhode Island, and that of the initial candidates, only seven were licensed. I blush to admit that it had to be pointed out to me that this was probably a reference to the first seven JLAers having their first HQ in Happy Harbor.
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Mount Justice! It's in Happy Harbor, Rhode Island. The JLA has had six origins, and off the top of my head, I'd say Mt. Justice was their first HQ in all of them. The membership varied, though. Your reference is to the first origin.