The Book of Mormon geography student should note that the ideas expressed in Alma 46:17 can be taken a number of ways. I will try to illustrate just three possibilities:
(1) And it came to pass that when he had poured out his soul to God, he [Moroni] named all the land which was south of the land Desolation [or in other words the Land Southward], yea, and in fine, all the Land [Southward] both on the north [Bountiful and Zarahemla] and on the south [land of Nephi] --A chosen land, and the land of liberty.
(2) And it came to pass that when he had poured out his soul to God, he [Moroni] named all the land which was south of the land Desolation [or in other words the land Bountiful], yea, and in fine, all the land [of the Nephites] both on the north [Bountiful] and on the south [Zarahemla] -- A chosen land, and the land of liberty.
(3) And it came to pass that when he had poured out his soul to God, he [Moroni] named all the land which was south of the land Desolation [or in other words all of the Land Southward], yea, and in fine, all the land [all of the continent] both on the north ["north" from the border of Desolation] and on the south ["south" from the border of Desolation] --A chosen land, and the land of liberty.
A fairly decent rational could probably be given for each of these interpretations, and maybe a multiple interpretation is in order. At present, I favor the second interpretation. It seems that Moroni, at this time, was trying to seek an answer as to how to preserve (or "establish"--Alma 45:22) the church. In Alma 46:13, Moroni "prays mightily unto his God for the blessings of liberty to rest upon his brethren, so long as there should a band of Christians remain to possess the land." At this point in time, the Lamanites had driven all the Christians out of the land of Nephi, and so the only places that Christians might be living were in the land of Zarahemla and possibly in the land of Bountiful. Therefore, once Moroni received the inspiration from the Lord, he was able to embark on his crusade and name the parameters of his mission. [Alan C. Miner, Personal Notes]