Joseph Smith and his followers declared the Book of Mormon’s supernatural origin—that it was a divinely inspired translation of an ancient-American record, acquired by Joseph through visions and the help of an angel. This explanation, however, was widely rejected by outsiders from the outset. Within weeks after the Book of Mormon’s first pages came off the press, critics promoted “naturalistic explanations”—so called because they are based on scientific observation or natural phenomena—that rejected the possibility of a divine, supernatural origin of the Book of Mormon. To varying degrees, these naturalistic theories continue to be perpetuated today. This article examines the most popular naturalistic explanations for the Book of Mormon longitudinally, which will enable readers to better understand them and why they have waxed and waned in popularity over time.