In following the travels of the descendants of Lehi since their arrival, the land of their inheritance was not far from where they landed. Subsequent migrations north to Zarahemla did were not an extensive distance. In fact, the distance between the lands of Nephi and Zarahemla could be traveled in only 21 days (Mosiah 23:3; 24:25), or an approximate distance of 300-400 miles. However, this Nephite excursion is different because of the great distance traveled. Significantly, the location of the large bodies of water and many rivers spoken of is not known, but it has been implicated to be in Central America (see Reynolds and Sjodahl, Commentary on the Book of Mormon, vol. 5, p. 207).
Hugh Nibley
“…the great northern migration [was] a massive drift of population, Nephite and Lamanite alike (Helaman 6:6), to lands far to the north. In the same year in which Hagoth sent off his first great ship to the north (Alma 63:5-6), a company of ’five thousand and four hundred men, with their wives and their children, departed out of the land of Zarahemla into the land which was northward’ (Alma 63:4). This was but the beginning of a continuing trend of large-scale migration into the north countries. Because of troubles and dissension a really great movement took place a few years later when ’an exceedingly great many … went forth unto the land northward to inherit the land. And they did travel to an exceedingly great distance, insomuch that they came to large bodies of water and many rivers’ (Helaman 3:3-4). This is obviously not to be confused with the northern land of lakes from which Moroni barred access to the people of Morianton in a relatively small-scale military action (Alma 50:25-35). When distance is described as ‘exceedingly great’ by a people to whom long marches and strenuous campaigns in the wilderness were the established rule, we can be sure that it was at least the equivalent of the migrations of some of our Indian tribes in modern times, which sometimes ran to thousands of miles. Once the Book of Mormon people break out of the land of Zarahemla, there is no telling how far they go: since they have all the time in the world we have no right to limit their wanderings and settlements by our own standards of foot-travel.” (An Approach To The Book of Mormon, p. 409)