The Book of Mormon claims that the American Indians are descendants of a lost tribe of Israel, and that this fact has some kind of eschatological significance. These ideas were not original to Mormon founder Joseph Smith, however.
Gordon and Popkin trace the origins and development of the so-called Jewish Indian Theory. Elias Boudinot was the most prominent believer in such a perspective, and in his book “Star in the West” he believes that the Indians will one day forcefully return to Jerusalem. They will also be converted to Christianity. Boudinot even founded an organization known as Society for the Amelioration of the Conditions of the Jews. The “Jews” were in fact the Indians. Even some Jews developed similar ideas, including prominent U.S. Jewish leader Mordecai Noah, who attempted to create a Jewish “state” at Grand Island outside Buffalo, to which he planned to invite the Indians.
Thus, when Joseph Smith burst onto the stage with his seemingly weird ideas about “Lamanites” descended from Biblical Israel, he wasn't really saying anything dramatically new.
For a closer look at this matter, readers are referred to Fawn Brodie's classic “No Man Knows My History”.