We now come to one of the big surprises in the entire Book of Mormon. As the next series of chapters unfold, we discover that two-thirds of the gold plates received by Joseph Smith were filled with the writings of Moroni and only one-third comprised the writings of Mormon. This interesting discovery was mentioned by Orson Pratt in Journal of Discourses3:347. We further learn that after Mormon was killed we estimate that it left Moroni alone for at least 25 to 30 years according to Moroni 10:1.
During all of those years Moroni had to scrounge for his food and live as a fugitive in hiding because the Lamanites were trying to find him and kill him. We also learn that it was during these lonely, treacherous years that Moroni found the gold needed to make additional plates. He then translated from the Adamic tongue the sweeping vision of the entire prophetic history of the world as seen by the brother of Jared. But Moroni sealed up this prophetic history after recording it on the gold plates so Joseph Smith could not translate it.
However, Moroni did not seal up the history of the Jaredites which we are now going to study. Moroni says the Jaredites inhabited the North America continent and turned out to be the greatest nation in ancient times. The Jaredites numbered in the millions and according to the record were the greatest nation in antiquity -- greater than Babylon, Persia, Greece or Egypt. Amazingly, today there is not a single survivor or even a descendant of the Jaredites left alive on the face of the earth. We will now study the history of this people which existed in America for nearly 2,000 years.
Moroni speaks of the "north country" which would seem to mean North America. This means that while the Jaredites were developing into a nation of millions of people in "north country," the Nephites and the Mulekites, which came separately from Jerusalem around 590 B.C., were developing in the "land southward" without any knowledge of the Jaredites to the north.
However, at a date surmised to have been around 250 B.C., the last survivor of the Jaredites came down into the land southward and stumbled onto the Mulekites. But he died "after nine moons" without being able to learn Hebrew particularly well to communicate with the Mulekites. The important thing to remember is that these nations existed simultaneously on the American continent from around 590 B.C. to approximately 250 B.C. without being aware of one another. Some scholars have tried to force the entire Book of Mormon history into a relatively small territory, but that doesn't seem to fit Moroni's description of what really happened.