“The Church was established in 1830, during an era of great racial division in the United States. At the time, many people of African descent lived in slavery, and racial distinctions and prejudice were not just common but customary among white Americans. Those realities, though unfamiliar and disturbing today, influenced all aspects of people’s lives, including their religion.
…In two speeches delivered before the Utah territorial legislature in January and February 1852, Brigham Young announced a policy restricting men of black African descent from priesthood ordination.
The justifications for this restriction echoed the widespread ideas about racial inferiority that had been used to argue for the legalization of black “servitude” in the Territory of Utah. According to one view, which had been promulgated in the United States from at least the 1730s, blacks descended from the same lineage as the biblical Cain, who slew his brother Abel.”
“Over time, Church leaders and members advanced many theories to explain the priesthood and temple restrictions. None of these explanations is accepted today as the official doctrine of the Church.”
…Today, the Church disavows the theories advanced in the past that black skin is a sign of divine disfavor or curse, or that it reflects unrighteous actions in a premortal life; that mixed-race marriages are a sin; or that blacks or people of any other race or ethnicity are inferior in any way to anyone else. Church leaders today unequivocally condemn all racism, past and present, in any form.”
See also: Historian’s Office reports of speeches, 1845-1885 / Brigham Young, 1852 January 23. (Additional Source link)