Added insight into the state of knowledge prior to Stephens' popular book comes from an 1841 review of Stephens' work found in The North American Review, Vol. 53, 1841, published by James Monroe and Company, Boston, available online through the Making of America section of the Cornell University Library, a resource that I have just recently encountered thanks to the same critic who has been contending that Mesoamerican details relevant to the Book of Mormon were well known in Joseph's day. It is true that an 1825 publication states that "At the time of the conquest it is well known, that Mexico was a city of great extent and splendor." Certainly this rather vague bit of information and more was known in some circles. The basic story of the Spanish conquest must have been well known. For more details about Mesoamerica, several Spaniards had written about Mexico, the German von Humboldt had published several works before Joseph Smith's day, and Ethan Smith cites von Humboldt several times, for example. But there is no evidence that Joseph Smith had access to this information, and reading these works shows no hint that they were relied on in producing the Book of Mormon. Indeed, if Joseph were familiar with all that and were fabricating the Book of Mormon, he missed many goldmines of information that could have been used to dress up the book and add to its plausibility.
Let's turn back to the review of Stephens' book, which begins on page 479 of the publication. Near the beginning of the review, on page 480, we have this comment regarding the ancient Mesoamericans and "the riddle of their history":
Now look at page 489:
The recent discoveries in Central America have attracted a new attention to these questions. The time for constructing a theory is not yet. The materials are still too scanty. But they are accumulating in great richness; and to no part of the world does the historical inquirer look with a more intense interest, than to that country, lately as little thought of as if it did not exist, now known to be so fruitful in marvels.
It would be all but incredible, if it were not now shown to be certainly true, that in the wilds of Central America are found vast architectural piles, with complicated decorations chiselled in hard stone, which, different as is their style, might without extravagance be called worthy of the best eras of European art. The "vast buildings or terraces, and pyramidal structures, grand and in good preservation, richly ornamented," struck Mr. Stephens on his first approach, as "in picturesque effect almost equal to the ruins of Thebes."Stephens is quoted on page 490 as he describes the experience of looking out over one of the ancient cities:
There is no rudeness or barbarity in the design or proportions; on the contrary, the whole wears an air of architectural symmetry and grandeur; and as the stranger ascends the steps and casts a bewildered eye along its open and desolate doors, it is hard to believe that he sees before him the work of a race in whose epitaph, as written by historians, they are called ignorant of art, and said to have perished in the rudeness of savage life.Stephens is challenging the day's common knowledge of Native Americans, showing that the architectural evidence points to an ancient people who were not rude savages or barbarians.
Also see page 491 and page 492, where we read an amusing illustration of the ignorance of the day. The reviewer quotes a passage from a competitor's journal that argues for the ignorance of learned men and the British public by pointing out how some allegedly new discoveries were previously documented by others (". . . we can adduce an extraordinary instance of the ignorance prevailing among literary and scientific men in general. . . . This circumstance is alone sufficient to show that the subject is, unlike Egyptian antiquities, comparatively new to the reading British public"), but the reviewer then points out that this is in fact a serious error and that Stephens' report of Copan appears to be the first - all of which only strengthens the case for the lack of widespread knowledge about Mesoamerica in that era among the learned, and certainly among the masses.
The point is not that Mesoamerica was completely unknown in 1830, but that it's unlikely that someone like Joseph Smith could have relied on common knowledge or even available publications for the information needed to even begin attempting a fraud that would include Mesoamerican features aimed at enhancing the plausibility of the text. There is simply no prima facie case to explain the Mesoamerican elements in the Book of Mormon as something that Joseph Smith could have fabricated based on what he could have drawn from his intellectual environment. To dismiss the Book of Mormon as the obvious product of fabrication based on common knowledge of that day is rather unreasonable, in my opinion. That doesn't prove anything, but one thing is clearly unproven: the theory that Joseph Smith fabricated the text.