The Book of Mormon relates the history of a group of Hebrews who migrated from Jerusalem to America about 600 BC, led by a prophet, Lehi. They multiplied and eventually split into two groups. One group, the Lamanites, forgot their beliefs, became heathens, and were the ancestors of the American Indians. The other group, the Nephites, developed culturally and built great cities but were eventually destroyed by the Lamanites about AD 400. Before this occurred, however, Jesus had appeared and taught the Nephites (after his ascension). The history and teachings were abridged and written on gold plates by the prophet Mormon. His son, Moroni, made additions and buried the plates in the ground, where they remained about 1,400 years, until Moroni, a resurrected being or angel, delivered them to Joseph Smith; subsequently Smith returned them to Moroni.

Non-Mormon critics disagree in their opinions as to the origin of the book; some critics believe that it was written solely by Joseph Smith. Another theory, now discredited, claimed that it was based on the manuscript of a novel by a clergyman, Solomon Spaulding.