(This is an excerpt from Mormon's Codex by John L. Sorenson.)
The geographical background of the Nephite record is revealed in information that the writers included only incidentally in their accounts. Some 600 statements in the record reflect the lay of the promised land. When these statements are exhaustively examined, they reveal that Mormon and all the earlier record keepers shared all or parts of the same mental map of their land. Some writers were directly acquainted with more areas and more details about the geography than others, but their statements never contradict one another. This consistency of information indicates that the authors had firsthand experience of a specific physical scene. Most notably, Mormon, the principal military commander of the Nephites during their final century and the author/compiler of the book, operated over most of that space and gave us particularly comprehensive map information.
The general “land of Nephi” was an upland physiographic unit. It is invariably said to be reached by traveling “up,” both from “the borders by the west sea” and from the land of Zarahemla. Consistency is also shown in references to the “river Sidon.” Its waters were considered to originate in a mountainous “narrow strip of wilderness” through which parties passed when going from Nephi to Zarahemla or vice versa. In early Nephite history, movements of parties within the land of Nephi were frequently through intervening and widespread “wilderness,” as though islands of civilization formed an archipelago scattered in a sea of uninhabited wilderness. In general, but not necessarily at every point in the text, the term wilderness connoted a forested area, judging by people’s ability to hide or get lost in it. In later parts of the narrative, the population had, of course, filled in more of the once-uninhabited areas and wilderness is less frequently mentioned. Because of the consistency with which features of the internal geography are mentioned, the book holds out the prospect that we can discover the actual physical geography based on statements in the text. In that case we then may be able to identify where in the real world the events of the record were played out.
That step requires, first of all, a synthesis of the internal geographical data. One such synthesis is summarized in chapter 2 and appears in greater detail in two previous books, The Geography of Book of Mormon Events and Mormon’s Map. Chapter 2 also summarized the next step—identifying the area in the New World that fits best the text-based geography. The most crucial data in making that correlation relates to the advanced cultural nature of the Nephites’ area as sketched in the text. There are many statements about cities, and even “great cities,” in the world of the Nephites. Large-scale wars were carried on; the size of the forces engaged means that the total population ranged upward to a few million. The historically documented groups were often literate; books were kept in multiple scripts.
It is evident that the Nephite lands were the home of a civilization. That being so, the area would have to be located in the civilized part of the ancient New World. Given also that a critical feature of their physical world was a narrow neck of land (isthmus) bounded by oceans, no geographical correlation can qualify except Mesoamerica or a portion of it, for only there were large cities, major populations and wars, and books found anciently around an isthmus. But more specifically, where within Mesoamerica can the record and its peoples have been located? Correspondences between physical details in Mesoamerica and in the Book of Mormon allow us to pin down the area involved.
(John L. Sorenson, Mormon’s Codex [Salt Lake City: Deseret Book, 2013], 119–20).