Historicity of the Book of Mormon
When Moroni visited Joseph Smith in September 1823, he "gave a history of the aborigenes [sic] of this country," "said this history was written and deposited not far from that place," [Joseph's home] and that it was Joseph's "privilege, if obedient to the commandments of the Lord, to obtain and translate the same by the means of the Urim and Thummim, which were deposited for that purpose with the record."
https://www.josephsmithpapers.org/paper-summary/history-1834-1836/69
Joseph taught that the Book of Mormon was an authentic history of real people. After crossing Ohio, Indiana and Illinois on his way to Missouri in June 1834, Joseph wrote a letter to his wife Emma. He explained that he and his company had been "wandering over the plains of the Nephites, recounting occasionally the history of the Book of Mormon, roving over the mounds of that once beloved people of the Lord, picking up their skulls & their bones, as a proof of its divine authenticity."
https://www.josephsmithpapers.org/paper-summary/letterbook-2/63
Later that year, in October 1834, an anti-Mormon book titled Mormonism Unvailed was published near Kirtland, Ohio. Among other things, the book claimed that the Book of Mormon was fictional, based on an unpublished novel by Solomon Spalding. Partly in response to this book, and with the assistance of Joseph Smith, Oliver Cowdery wrote a series of essays about the early history of the Church. He published the essays as letters in the Messenger and Advocate, a Church newspaper in Kirtland. In Letter VII, he described the location of the hill affirmed that it was a fact that the hill Cumorah in New York is the same hill as the hill Cumorah in Mormon 6:6; i.e., the scene of the final battles of the Nephites and the Jaredites.
At about one mile west rises another ridge of less height, running parallel with the former, leaving a beautiful vale between. The soil is of the first quality for the country, and under a state of cultivation, which gives a prospect at once imposing, when one reflects on the fact, that here, between these hills, the entire power and national strength of both the Jaredites and Nephites were destroyed.
By turning to the 529th and 530th pages of the book of Mormon120 you will read Mormon’s account of the last great struggle of his people, as they were encamped round this hill Cumorah.
https://www.josephsmithpapers.org/paper-summary/history-1834-1836/90
Joseph had his scribes copy these essays into his own journal as part of his life history. He approved their republication in 1841 in both the Gospel Reflector and the Times and Seasons. His brother William republished them again in 1844 in the New York newspaper called The Prophet. They were also republished in England in the Millennial Star and in Utah in the Improvement Era.
Some Latter-day Saint scholars disbelieve what Oliver wrote in Letter VII. They claim instead that the "real Cumorah" must be in southern Mexico (Mesoamerica) and that the hill in New York was named Cumorah erroneously because of a false tradition. In so doing, they claim Lucy Mack Smith, David Whitmer, Martin Harris, and others went along with Joseph and Oliver in perpetuating this false tradition, and that all the LDS leaders who reaffirmed the location of Cumorah, including members of the First Presidency speaking in General Conference, have been wrong.
Other Latter-day Saints still believe what these prophets have taught about Cumorah.
For a summary of those teachings, see https://www.mobom.org/hill-cumorah
This page offers comparisons for you, the reader, to consider as you make your own informed decisions.
Table comparing 1 New York Cumorah to M2C
