If you figure you better learn a little something about Mormonism, you could do worse than begin with chapter 8, "Archaeology and Religion," in Stephen Williams's Fantastic Archaeology: The Wild Side of North American Prehistory. Williams offers a restrained, if brief, presentation of Mormonism's roots in the archaeological speculations of Joseph Smith's time. Because I try (though often fail) to always make connections between religion and sf on this blog, I must mention that one of Williams's most important sources for this chapter is the nonfiction work, Moundbuilders of Ancient America, by Robert Silverberg, who is better known for his science fiction.
To make a brief summary of Williams's explanations, Joseph Smith is a difficult person to research, for few dispassionate biographies exist: almost everyone who writes of him either saints him or vilifies him (Williams 1991:159).
In 1827, Smith claims to have found, through divine revelation, a set of gold plates buried on Hill Cumorah in New York State (Williams 1991:161). If I'm not mistaken, this is a part of the so-called "Burned-Out Zone" or "Burned-Over District," which experienced a curious proliferation of new religious movements in the nineteenth century (here's a Wikipedia article on it, to which I must append a warning: no more likely to be accurate than the blog you're reading).
Steve Wood, a Catholic apologist, has suggested that the religious detritus of the Burned-Over District was the aftermath of Evangelical revivalist evangelism methods. In other words, the fractured new religious movements that appeared in the Burned-Over District are the product of Evangelicalism's inherent theological instability, which becomes most obvious during its periods of greatest energy. Joseph Smith's own account of what led to his first vision tends to support Wood's assertion: as I read Smith, he was frustrated with the quarrels between different Protestant sects and felt he had no means to choose between them, so he finally gave up on all of them and founded his own. Although Catholics don't grant Mormons the title "Christian," I think Smith probably deserves no more blame that Luther, though he may deserve more admiration for his greater creativity.
Along with the plates, Smith recovered the Urim and Thummin, which he used to interpret the plates, which were inscribed in "reformed Egyptian," whatever that is (Williams 1991:162-163). Already, Mormonism hits a serious archaeological snag. There's no such thing as reformed Egyptian (Demotic, maybe?), though I will posit the wild guess that Smith was aiming here for a language the Israelites might have borrowed from Egypt and altered after the Exodus. A set of reformed Egyptian characters allegedly copied from one of the plates does exist, but scholars regard it as a nonsensical jumble (Williams 1991:163).
Williams does not discuss the Urim and Thummin at any length, but I should comment on those as well. Josephus depicts them as glowing jewels (in Antiquities iii.8.9, according to the Brown-Driver-Briggs Hebrew and English Lexicon p. 22) and the Dead Sea Scroll sometimes entitled "Tongues of Fire" depicts them this way as well (texts 1Q29 and 4Q376, which you can find on p. 178 of The Dead Sea Scrolls: A New Translation). Philo describes the Urim and Thummin as embroidered images sewn to a bag used to carry them (Brown-Driver-Briggs again, p. 22). Most scholars today assume the Urim and Thummin were something like dice used for casting lots. As far as I know, the concept of the Urim and Thummin as lenses to look through in order to read ancient texts is original to Mormonism.
One of the basic idea of Mormonism, that the Moundbuilders of the Ohio Valley were from the Lost Tribes of Israel (Williams 1991:164-165), is not original to Smith but was a popular notion at the time, though it, like other Lost Tribes legends, is now out of favor with scholars. Williams mentions an interesting development in Mormonism: Smith imagines grand civilizations that are lacking in New York, so modern Mormonism usually depicts the events of the Book of Mormon taking place in Mesoamerica, though this is clearly not Smith's original intent (Williams 1991:166).
Thus when archaeology was finally brought into the Mormon question, it was usually with regard to the high cultures of Mesoamerica and Peru. Today Mormon literature, including my copy of the Book of Mormon, is illustrated with color pictures of copper, bronze, and gold artifacts from Peru and with temples from Mexico, not Ohio Valley Moundbuilder relics. Christ is shown visiting the New World in the midst of a ceremonial plaza with a broken Maya stela on one side.... [Williams 1991:166]
So, there you go. There's more, but I recommend you grab the book and read it yourself. Tomorrow, I'll discuss some other interesting elements in the chapter.
1991. 8. "Archaeology and Religion: Where Angels Fear to Tread" in Fantastic Archaeology: The Wild Side of North American Prehistory 156-188. University of Pennsylvania Press, Philadelphia.