It came from Moroni himself.
Note 22 cites Lucy Mack Smith, History, 1844–45, book 3, –. You can see this online at the Joseph Smith Papers here: https://www.josephsmithpapers.org/paper-summary/lucy-mack-smith-history-1844-1845/40
Lucy's explanation of Cumorah is found on the very next page of Lucy's history. Lucy Mack Smith, History, 1844–45, book 3, . You can see this online at the Joseph Smith Papers here:
[Moroni, after telling Joseph about the record, said] but you cannot get it until you learn to keep the commandments of God For it is not to get gain. But it is to bring forth that light and intelligence which has been long lost in the Earth
Now Joseph beware or when you go to get the plates your mind will be filled with darkness and all manner of evil will rush into your mind. To prevent you from keeping the commandments of God that you may not succeed in doing his work and you must tell your father of this for he will believe every word you say.
The record is on a side hill on the Hill of Cumorah 3 miles from this place. Remove the grass and moss and you will find a large flat stone pry that up and you will find the record under it laying on 4 pillars of cement— then the angel left him. [editing marks removed]
In my Letter VII post, I pointed out that Lucy's description of what Moroni told Joseph is highly credible because of the detail and description it contains. She explained that Moroni referred to the hill by name and specified its location. Moroni told Joseph he'd have to remove the grass and moss, which is a significant detail because it helps explain why the stone had not been removed in the centuries since Moroni first put it over the stone box.
There's another important reason why Lucy's account is credible.
Some scholars reject what Lucy wrote because she seemed to conflate the first vision with Moroni's visit.
But that's the opposite conclusion that follows from the facts.
It's true that, if you read Lucy's account, it looks as though she is conflating the two accounts (see her account below, without the editing marks).
What Lucy dictated is the opposite of what she would have dictated if she was conflating memories with modern developments. By 1844-5, Joseph's account of the First Vision was well know. What is now Joseph Smith-History had been published in the Times and Seasons in 1842. If Lucy was incorporating more modern events (such as the New York Cumorah) into her history, as the M2C scholars claim, then she surely would have incorporated Joseph's formal description of the First Vision.
In fact, in the 1845 version of Lucy's history, created by the Corays from Lucy's original version plus additional material (see the historical introduction), the Corays (without explanation) actually replaced Lucy's account by incorporating the History of Joseph Smith that was published in the Times and Seasons.
This indicates that Lucy's reported what she remembered, not what people wanted or expected her to remember.
There is no indication that Joseph told his mother specifically about the First Vision prior to the visit of Moroni. In his 1832 history, Joseph wrote that he "could find none that would believe the hevnly vision nevertheless I pondered these things in my heart
about that time my mother and20."
Note 20 reads, "This canceled fragment may refer to the Presbyterian affiliation of JS’s mother and three of his siblings."
When Joseph described Moroni's visit, he said "he called me by name and he said the Lord had forgiven me my sins and he revealed unto me that in the Town of Manchester Ontario County N.Y. there was plates of gold upon which there was engravings which was engraven by Maroni & his fathers."
That is consistent with what Lucy dictated.
To repeat: If we accepted Lucy's account, then we know the origin of the New York Cumorah narrative.
It came from Moroni himself.
Lucy's original dictation:
One evening we were sitting till quite late conversing upon the subject of the diversity of churches that had risen up in the world and the many thousand opinions in existence as to the truths contained in scripture Joseph never said many words upon any subject but always seemed to reflect more deeply than common persons of his age upon everything of a religious nature
After we ceased conversation he went to bed and was pondering in his mind which of the churches were the true one. but he had not laid there long till he saw a bright light enter the room where he lay he looked up and saw an angel of the Lord standing by him
The angel spoke I perceive that you are enquiring in your mind which is the true church there is not a true church on Earth No not one and has not been since Peter took the Keys of the Melchesidec priesthood after the order of God into the Kingdom of Heaven the churches that are now upon the Earth are all man made churches.
There is a record for you and Joseph but you cannot get it untill you learn to keep the commandments of God For it is not to get gain. But it is to bring forth that light and intelligence which has been long lost in the Earth Now Joseph beware or when you go to get the plates your mind will be filld with darkness and all manner of evil will rush into your mind. To prevent you from keeping the commandments of God that you may not suceced in doing his work and you must tell your father of this for he will believe every word you say the record is on a side hill on the Hill of Cumorah 3 miles from this place remove the Grass and moss and you will find a large flat stone pry that up and you will find the record under it laying on 4 pillars of cement— then the angel left him
The next day he and his father Alvin [Smith] were reaping in the field togather sudenly Joseph stopped and seemed to be in a deep Study for some time Alvin hurried him saying Joseph we must keep to work or we shall not get our task done Joseph worked again dilligently then stopped in the same way a second time when his father Saw that he was very pale and urged him to go to the house and tell his mother that he was sick he went a short distance till he came to a green sward under an apple tree here he lay down on his face for he was so weak he could go no farther. *
The personage whom he saw the night before came to him again and said why did you not tell your father what I told you Joseph said he was affraid his father would not believe him he will said the angel believe every word you say to him he then told when you get the record take it immediately into the house and lock it up as soon as possible and let no one see it till it is translated and then show it to such as the Lord chooses as a witness to the world