There remain some Latter-day Saints who think the "real" Hill Cumorah is somewhere in southern Mexico. In fact, next month a group of Mesoamerican activists are holding a conference to try to persuade people of this idea. I'll comment more about that in coming posts.
It's comical, really.
The New York location of the Hill Cumorah has been known since before Joseph even got the plates. In one part of the hill was the stone and cement box that Moroni constructed to put the abridgment. But in a separate area of the hill, Mormon "hid up" all the other Nephite records.
Here's a graphic to depict this:
Here is how Orson Pratt explained it:
“The prophet Mormon, the father of Moroni, had been entrusted with all the sacred records of his forefathers, engraved on metallic plates. New plates were made by Mormon on which he wrote...
“These new plates were given to Moroni to finish the history, and all the ancient plates Mormon deposited in Cumorah, about 384 years after Christ. When Moroni, about thirty-six years after, made the deposit of the book entrusted to him, he was, without doubt, inspired to select a department of the hill separate from the great, sacred depository of the numerous volumes hid up by his father.
“The particular place in the hill, where Moroni secreted the book, was revealed by the angel to the Prophet Joseph Smith, to whom the volume was delivered in September, 1827. But the grand depository of all the numerous records of the ancient nations of the western continent, was located in another department of the hill, and its contents under the charge of holy angels, until the day should come for them to be transferred to the sacred temple of Zion.”
Orson Pratt, “The Hill Cumorah,” Millennial Star, Vol. 28, July 7, 1866, p. 417