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"A Narrow Strip of Wilderness"

"...the king sent a proclamation...amongst all his people who were in all his land...which was bordering even to the sea, on the east and on the west, and which was divided from the land of Zarahemla by a narrow strip of wilderness, which ran from the sea east even to the sea west, and round about on the borders of the seashore, and the borders of the wilderness which was on the north by the land of Zarahemla, through the borders of Manti, by the head of the river Sidon, running from the east towards the west—and thus were the Lamanites and the Nephites divided."  (Alma 22:27)  90 B.C.-77 B.C.

1st.   This "narrow strip of [mountainous] wilderness" must run and does run from the "sea east to sea west".
2nd.  A east sea and a west sea must and does mark the two ends of this "narrow strip of wilderness".
3rd.   A major river must and does have its source in this same "narrow strip of wilderness".  [The Grijalva River has its source in this mountain range.]
4th.   At least some of this river must and does run from "the east toward the west" at a source point.  [Part of the Grijalva River runs from the east toward the west.]
5th.   Also some kind of evidence that a civilization with a written language must and does exist in that location during the same time periods as recorded in the Book of Mormon. 

"A Narrow Strip of Wilderness" - Map (Yucatan Peninsula)

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 There should be no wonder why this mountain range would be in fact a barrier and protection for the Nephites on the North from the Lamanites on the South.
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 "...the Nephites in their wisdom, with their guards and their armies, had hemmed in the Lamanites on the south, that thereby they should have no more possession on the north, that they might not overrun the land northward."  (Alma 22:23)

"...the Nephites had taken possession of all the northern parts of the land bordering on the wilderness, at the head of the river Sidon, from the east to the west, round about on the wilderness side; on the north...."  (Alma 22:29)