Plural Marriage
From MormonWiki
At one time in its early history, the Church endorsed a form of polygamy called "plural marriage," but this is no longer the case. Joseph Smith, Brigham Young and other early members and leaders of the Church were married to more than one wife. The practice was officially withdrawn as stated in a declaration called "The Manifesto" which was given by President Wilford Woodruff in 1890 (see Official Declaration 1), and which advised Church members to obey the marriage laws of their land. Members of The Church of Jesus Christ of Latter-day Saints who engage in multiple marriage relationships are excommunicated.