Mormon in a detailed geographical account places the river Sidon along the northern extent of the narrow strip of wilderness, which served as the northern boundary of the Lamanite lands (Alma 22:27–34). This border region, in turn, also served as the southern limit of the Nephite lands. Mormon twice mentions a prominent feature of the river Sidon, “the head of the river Sidon,” when describing the contentious border that “divided” the Lamanites and Nephites and positions the river Sidon and its “head” relative to the land of Zarahemla and the other Book of Mormon lands, such as the land of Nephi (Alma 22:27, 29).

When Lamoni’s father, the king of the Lamanites, converted to the gospel through the preaching of Aaron, one of the sons of Mosiah, he sent a proclamation to all his people declaring the four sons of Mosiah could preach the gospel in all parts of the land, without hinderance. Mormon, at this point in his abridgment, pauses his narrative and inserts a detailed description of the converted king’s land, including a description of the land of Nephi, the land of the people of Zarahemla and the lands previously occupied by the Jaredites (Alma 22:27–34). No explanation for the inclusion of these geographical positioning scriptures (GPS) is given. However, these eight verses, providing some 20 geographical details, in sequence, are without equal for finding and matching a proposed location for the Book of Mormon story. In these non-abridged verses, Mormon in his own words defines the shape of the combined land area, the relative location of the lands within the larger area and the spatial location of wilderness regions, the small neck of land, the river Sidon and the west and east seas.

We suggest any proposed location for the Book of Mormon lands—including the positioning of the river Sidon—would be required to pass the test of fully matching these 20 geographical descriptions recorded by Mormon. In our main article, An Approach to the Book of Mormon Geography, under the subtopic, "Mormon’s Description of Book of Mormon Lands", we illustrate with several maps the results of our correlating these 20 geographical points to the area and landforms of Baja California. We recommend the reader view these maps point by point, while studying the corresponding scripture text. We propose the configurations and alignments of the Baja California peninsula, including the location of the Rio San Ignacio (the river Sidon), fully match the geographical points in Mormon’s description of the Book of Mormon lands (see also, Mormon’s Description of the Book of Mormon Lands, a video presentation on our web site).

The land of Zarahemla is positioned by Mormon in the area north of the narrow strip of wilderness, with the river Sidon on its border (Alma 22:27). A “round about” Lamanite-held cape figures prominently in the demarcation of the borders dividing the Lamanites and Nephites (Alma 22:27–28). Three Nephite-held lands—Zarahemla, Bountiful, and Desolation—extend in sequence towards the north (Alma 22:29–33). The Jaredites before their destruction possessed the land of Desolation (Alma 22:30). The people of Zarahemla (the people of Mulek) initially landed in this northern area and then moved south to a place they called the city and land of Zarahemla, located to the north of the narrow strip of wilderness (Alma 22:30–31). The land of Nephi is positioned to the south of the narrow strip of wilderness (Alma 22:28, 33–34). Mormon’s description leaves little question as to the river Sidon’s relative location within the center of the north-south trending Book of Mormon lands. And this pivotal location accurately matches the position of the only river of significance within central Baja California—the Rio San Ignacio.

Mormon wrote these 20 geographical descriptions as a supplement to his abridgment in about A.D. 385, some 460 years after the missionary event he was recording (between 90 and 77 B.C.). It is noteworthy that Mormon does not mention any changes to the configuration of the lands in the intervening 460 years, such as the wide-scale destruction which took place at the time of the Savior's crucifixion, when “the whole face of the land was changed” (3 Ne. 8:12). It would appear these changes to the surface of the land did not adversely affect the shape and locations of the larger land configurations mentioned in Mormon’s narrative, and the geographical descriptions, including the location of the river Sidon, were still accurate and identifiable in his day.