Plates of Nephi

"[1] Nephi's father, Lehi, was also a prophet who, after prophesying of the destruction of Jerusalem, left with members of his extended family around 600 BC and was eventually directed to the New World.

Although the large plates were intended for the more secular history of the Nephites, it is obvious from the version available in the Book of Mormon that there was a good deal of spiritual content as well, including sermons, prophecies and moral lessons.

Whether the uneven coverage is a reflection of the original record or is an artifact of Mormon's abridgement is not clear from the text.

Joseph Smith recorded, in the Doctrine and Covenants, sections 3 and 10, that the Lord instructed him not to re-translate the portion of the book that was lost but to continue forward.

In place of the lost Book of Lehi, the translation from the small plates of Nephi was used, which covered the same time period.

The aforementioned sections of the Doctrine and Covenants (D&C 3, D&C 10) state that the loss of the Book of Lehi was foreseen by the Lord and that it was for this purpose that the small plates were provided.