In June of 1834 during the Zion’s Camp march to Missouri, a few members of the march discovered human bones about a foot underneath the surface of a mound. Joseph Smith stated that they were the bones of Zelph, a white Lamanite. Seven members of the camp recorded the experience that day, each one differing from the others. Dr. John Lund, citing Kenneth Godfrey, notes that all the accounts agree on the following points:
1. On June 2, 1834, members of Zion’s camp, traveling through Illinois, unearthed skeletal remains of a man near the top of a large burial mound.
2. Joseph Smith learned what he knew about the skeletal remains by way of a vision after the discovery.
3. The man was a white Lamanite named Zelph, a man of God and a great warrior who served under a known leader named Onandagus.
4. Zelph was killed in a battle with the Lamanites by the arrow found with his remains. 
Some scholars argue that the original recorded version of the Zelph incident was corrected by Joseph Smith and that the flawed account is the one that was included in the History of the Church—thereby casting doubt on the account’s accuracy. Although changes were made in the Zelph story,  they do not alter the basis of the claims of the incident that Lamanites and prophets lived in North America (interpreted hereafter as the United States).
John A. Widstoe believed that the Zelph incident had no bearing on Book of Mormon geography. He states: “This is not of much value in Book of Mormon geographical studies, since Zelph probably dated from a later time when Nephites and Lamanites had been somewhat dispersed and wandered over the country.” 
I find it interesting that Joseph Smith never specifically mentioned the Zelph incident to anyone. He may have been referencing the incident when he wrote Emma the following day about wandering over the “plains of the Nephites”  and picking up skulls as an authentication of the Book of Mormon, but he never mentions an ancient warrior named Zelph and a previously unknown prophet named Onandagus. Joseph’s private letter to Emma is the closest we have of Joseph recording the Zelph event.
“The longest and most detailed near-contemporaneous account of Zelph’s discovery was written by Levi Hancock.”  In his version, he makes mention that Joseph Smith stated, while under inspiration, that “This land was called the Land of Desolation.”  If Joseph Smith were speaking about the same “Desolation” mentioned in the Book of Mormon, this statement would place Zarahemla, Bountiful, Manti, and most other Book of Mormon cities south of this area (a location about where Valley City, Illinois, now is located) and would place the Book of Mormon too far south for a Great Lakes geography. If we accept the Zelph accounts as fact, we must also accept the implications of the story as well. Placing the land Desolation in Illinois automatically places most of the Book of Mormon events south of there, thereby eliminating most North American theories as plausible options.
So what are we to think of Zelph? We have a few options. Either those events mentioned by Joseph Smith transpired from the last battles as the Nephites were being pushed northward by the Lamanites or Nephites and dissenters of those who took on the name “Lamanites” had migrated north from Nephite lands. Fletcher Hammond argues that “it is possible and quite probable, that sometime during the Book of Mormon history, some adventurous Nephites and Lamanites settled in what is now the western plains of the United States, the Mississippi Valley, and as far north as the Great Lakes region. But, no account of what they did was important enough for Mormon to include it in the abridgment of the Large Plates of Nephi.” 
Another scholar, Norman Pierce, asks: “Why were the prominent chieftain Zelph and the great Prophet Onandagus, who was known from the eastern sea to the Rocky Mountains, not mentioned at all in the Book of Mormon? Surely a prophet of such prominence would have received some notice had he been known to the historians of the Book of Mormon. The answer is very obvious:—Because the Book of Mormon historians who were down in Central America, knew nothing at all of either the Prophet Onandagus or [of] the Chieftain Zelph. It was more than 400 years before Mormon’s time that Hagoth sailed north, and we only have a report of the first ship returning. . . . Naturally, both Mormon and Moroni were too far removed from Onandagus and Zelph to report them.” 
That reasoning seems to make sense. The Book of Mormon speaks about several migrations to the north. For example, Alma 63:4–9 recounts the migration of “five-thousand and four hundred men, with their wives and their children” from Zarahemla to the “land which was northward.” That same year, Hagoth built a “large ship” and sailed “into the land northward.” That ship returned and was filled again, as well as many “other” ships that were built and again sailed “northward.” In the thirty-ninth year, another ship sailed northward carrying provisions to those who had previously left, and it did not return.
So where were the tens of thousands of these people going? They possibly migrated to areas that Joseph Smith was claiming as Nephite territory. We have evidence of contact and migrations between Mesoamerica and what is now known as the United States dating to Book of Mormon time periods. Trade occurred between Mesoamerica and the eastern United States possibly as early as 200 BC.  Perhaps rumors came back to the Nephites from these traders about a land with good soil and mild summers, which caused these mass migrations northward. Also, many people would probably want to find a new land to live in after years of bloodshed and war with the Lamanites. That is, they may have wanted to escape the continuous warring and move to a new land to find peace. Whatever the reason may have been, thousands of Nephites departed out of the land of Zarahemla and moved northward. Interestingly, archaeologists report a major influence of Mesoamerican social ideas and building structures,  “and there are similarities between certain religious beliefs, legends, origin of stories, and symbols of the eastern Woodlands and Mesoamerica.” 
One scholar “wondered if Mississippian culture spread up the Mississippi floodplain carried on the backs of 'southern traders' who moved along a riverine 'highway' that might even have seen some travelers from Mesoamerica. Certainly there are many known instances in other parts of the world of dramatic political events and the founding of dynasties associated with the arrival of foreign lords or 'stranger-kings' who immigrated to new lands and super-imposed their wills and sense of order over those already there.”  Although the Mississippian culture postdates Book of Mormon times, the knowledge of these routes may have been well known in Book of Mormon times. Trade had been happening between Mesoamerica and North America for centuries before the Lehites even entered the Americas. There is evidence of similar migrations of traders from Mexico who settled in northeastern Louisiana at a place called “Poverty Point” (1650–700 BC), predating The Book of Mormon by at least a hundred years.
Archaeologist James A. Ford contends that Poverty Point flourished during a pivotal era when hunting and dispersed small camps were giving way to farming and settled towns. Ford also suggests that "Poverty Point was settled by Mexican Indian traders who crossed over by way of the Gulf of Mexico.” 
We also have Mesoamerican influence in North American cultures that are contemporary with the Book of Mormon. These same cultures (namely the Hopewell) have been thought by some North American theorists to be Book of Mormon peoples:
“The early appearance of Mesoamerican cultigens in eastern North America raises the question of whether the emergence of ranked societies, first in the Ohio valley (Adena and Hopewell), then in the Mississippi Valley, would have occurred if there had not been significant influences from the south. At present, the paucity of maize finds in Ohio and Illinois Hopewell sites suggests that cultivation of Mesoamerican crops was a minor part of Hopewellian subsistence base. Few other traits of Hopewell culture appear to be specifically Mexican; copper ear spools and panpipes might be markers of southern influence.” 
We should also note that the Zelph mound had some archaeological excavations in the 1870s and 1880s when many relics were found, as well as the discovery of “some connection with other geographic areas such as Michigan and Mexico.”  If this is the case and if Mesoamerican migrations and influence occurred up the Mississippi to the Hopewell and other cultures, then Joseph Smith would have been 100 percent correct in his assertions of Book of Mormon peoples living in North America. These people would have been satellite groups of the Nephites/Lamanites and not necessarily the same groups as recorded in the Book of Mormon. 
1. “Zelph,” Book of Mormon Referenece Companion, ed. Dennis L. Largey (Salt Lake City: Deseret Book, 2007), 801–2.
2. Kenneth W. Godfrey, “What Is the Significance of Zelph in the Study of Book of Mormon Geography?” Journal of Book of Mormon Studies 8, no. 2 (1999): 70–79.
3. John A. Widstoe, Improvement Era, July 1950, 547.
4. Dean C. Jessee, The Personal Writings of Joseph Smith (Salt Lake City: Deseret Book, 1984), 324.
5. Godfrey, “What Is the Significance of Zelph in the Study of Book of Mormon Geography? 70–79.
6. Levi Hancock Journal, LDS Church Archives.
7. Fletcher B. Hammond, Geography of the Book of Mormon (Salt Lake City: Utah Printing, 1959), 151–52.
8. Norman C. Pierce, Another Cumorah: Another Joseph (n.p.: Pierce, 1954), 35–36.
9. “Maize (Zea mays), the first Mesoamerican domesticate to reach ENA (Eastern North America), did not arrive for another 1,500 years, at ≈200 BC.” (Bruce D. Smith et al., “Initial Formation of an Indigenous Crop Complex in Eastern North America at 3800 B.P.” PNAS 2009, 106:6561–6566.
10. “Unmasking the Maya: The Story of Sna Jtz’ibajom,” Smithsonian Institution, National Museum of Natural History, Department of Anthropology, http://anthropology.si.edu/maya/mayaprint.html (accessed May 30, 2008).
11. Timothy R. Pauketat, Ancient Cahokia and the Mississippians (Cambridge: Cambridge University Press), 72. We note that the Cahokia postdate Book of Mormon peoples, but that dating does not negate an earlier Mesoamerican influence. Hundreds of years would be required to influence significantly a large culture with new beliefs.
13. Peter Nabokov, Native American Architecture (Oxford: Oxford University Press, 1989), 97.
14. Stuart J. Fiedel, Prehistory of the Americas (Cambridge: Cambridge University Press, 1992), 353.
15. Donald Q. Cannon, “Zelph Revisited,” Regional Studies in Latter-day Saint Church History: Illinois (Provo, UT: Brigham Young University Department of Church History and Doctrine, 1995), 97–109.
16. See also Cannon, “Zelph Revisited,” 97–109; FAIR’s review of “DNA Evidence for Book of Mormon Geography” http://www.fairlds.org/DNA_ Evidence_for_Book_of_Mormon_ Geography/DEBMG03 (accessed May 21, 2009); and Kenneth W. Godfrey, “The Zelph Story,” BYU Studies (Spring 1989): 31–56.