Death of Joseph Smith's brother Alvin from a physician's overdose of calomel. Shortly thereafter the family lost their farm. "One of the pivotal events in the lives of Smith family members was the death of Alvin Smith. Both Joseph Smith and Lucy Smith perpetuated an incorrect date for Alvin's death, believing that it had occurred in 1824. Alvin Smith's gravestone at Palmyra's General John Swift Memorial Cemetery confirms his death date as 19 November 1823."
[Alvin Smith Gravestone, 19 November 1823, General John Swift Memorial Cemetery, Palmyra, New York., as cited in Dan Vogel, Early Mormon Documents: Alvin Smith Gravestone]