Nauvoo was a period of significant religious and social innovations for the Latter Day Saints, beginning in 1840 with the introduction of vicarious baptisms on behalf of the deceased. Joseph Smith, concerned over the eternal welfare of his deceased brother, Alvin, but convinced of the necessity of saving ordinances, reconciled a seemingly-contradictory belief in both universal and sacramental salvation by introducing the vicarious baptism. Smith justified the practice by referencing a cryptic Biblical passage in the Epistles of Paul that alluded to baptism for the dead being practiced in the ancient church (1 Cor. 15:29). The practice was adopted with zeal by the Mormons who would spend countless hours in the Mississippi River baptizing on behalf of loved ones whose souls they feared were lost for eternity without receiving what they perceived as an essential rite.
At first, the practice was not well-defined. Virtually no record was kept of who received baptism. Furthermore, men were baptized on behalf of women and women on behalf of men, a practice that was later made gender-specific. The following year, Smith instructed his followers to cease conducting vicarious baptisms until they had completed a font to be placed inside of the Nauvoo temple, hoping to spur on its lagging construction. This change linked vicarious work with temples, which began shifting the function of LDS temples from primarily administrative and worship spaces to sacred spaces dedicated to the performance of religious ordinances.