In order to more fully appreciate what Alma 22:28-29 might be saying, we should review for a minute the meaning of the term "Lamanite." In 2 Nephi 5:6, speaking of those people who followed him (Nephites), Nephi said: "And all those who would go with me were those who believed in the warnings and the revelations of God; wherefore, they did hearken unto my words." Therefore, we can consider as "Lamanites" all the people existing at that time that didn't follow Nephi. This could have included the remnants of the Jaredite nation, the apostate Mulekites, the people who followed Laman and Lemuel, plus any other people native to the American continent at the time.
We are not told anything about this "drive" to move the "Lamanites" into this area "on the east by the seashore." In the general land of Zarahemla, this "drive" might have been due to the cultural pressures of having the Nephites under Mosiah1 migrating into the land of Zarahemla. The reader should note that later we see that Moroni drove the Lamanites completely out of this area on the east! (see Alma 50:9). But, in order to paint a picture of what Nephite lands were like at this particular time, Mormon states the following here in Alma 22:29:
. . . And thus the Nephites were nearly surrounded by the Lamanites; nevertheless 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, even until they came to the land which they called Bountiful.
[Alan C. Miner, Personal Notes] [See Geographical Theory Maps]
Geographical [Theory Map]: Alma 22:29 The Nephite Possessions (4th Year)
Reasonable Geographical Assumptions
At the time of the missionary travels of the sons of Mosiah to the Lamanites ("From about 91 to 77 B.C."--chronological footnote), Mormon inserts a commentary (Alma 22:27-34) into the text concerning the extent of lands then ruled by the converted Lamanite king. In this commentary Mormon says:
Now the more idle part of the Lamanites lived in the wilderness and dwelt in tents, and they were spread through the wilderness on the west in the land of Nephi, yea and also on the west of the land of Zarahemla in the borders by the seashore, and on the west in the land of Nephi, in the place of their father's first inheritance, and thus bordering along by the seashore. And also there were many Lamanites on the east [east in the land of Nephi and/or east of the land of Zarahemla] by the seashore whither the Nephites had driven them." (Alma 22:28-29)
From this commentary, one might make some reasonable internal assumptions:
(1) Although from their landing site on the coast, Nephi and his followers went inland and "up," the term "land of Nephi," as used in Alma 22:28-29, seems to imply a land which extended beyond a local highland area.
(2) According to Alma 8:7, "it was the custom of the people of Nephi to call their lands, and their cities, and their villages, yea, even all their small villages, after the name of him who first possessed them . . ." Thus the term "land of Nephi" as found in this Nephite record tends to be associated with an area that was apparently first "possessed" (ruled over?) by Nephi1 (or possibly by future Nephite kings who took upon themselves the name Nephi--see Jacob 1:11).
(3) If the Nephites drove the Lamanites all the way to the eastern shore, then surely the Nephite lands extended almost that far. Just when the Lamanites were "driven" is not mentioned, but what is more important here is the idea that the Lamanites were "driven" and the Nephites apparently took what land they desired. In Jarom 1:7 we apparently find the same situation. There it says that the Nephites "withstood the Lamanites and swept them away out of our lands . . . or whatsoever place of our inheritance."
(4) If the "idle Lamanites" resided "on the west in the land of Nephi" . . . "in the borders by the seashore," then the "land of Nephi" apparently included the "borders by the seashore."
(5) If the place described as "the place of their father's first inheritance" was "on the west in the land of Nephi" and "bordering along by the seashore," then one might reasonably presume that "the place of their father's first inheritance" was located in the land of Nephi and also "by the seashore."
Mormon's commentary on the Lamanite occupation of "the land of Nephi" also begs the following questions:
(1) Is it possible that after Mosiah's departure the Lamanites took over the rule of lands which had previously been ruled over by Nephite kings?
(2) If Lamanites took over the rule of Nephite lands, can one say that they began to rule over "the land of Nephi"?
(3) Since "the land of their father's first inheritance" was "in the land of Nephi," did the Lamanites begin to rule over a "land of Nephi" in which they had always been living?
As far as I am concerned, part of the answer to these questions might lie in how we define "idle Lamanites." If the "idle" part of that term pertained to their political and military activity, or in other words, if by "idle" they were "non-productive" both politically and to some extent militarily, then it is possible that these Lamanites had always been part of what is termed by Mormon "the land of Nephi," and to a large extent had been controlled by the Nephites. [Alan C. Miner, "Izapa: A Response to the Question of Geography," Unpublished]