Note: The Church of Jesus Christ of Latter-day Saints does not currently practice plural marriage. Please see the revelation on this subject.
Plural marriage was likely revealed to the Prophet Joseph Smith by 1831.
Joseph F. Smith, son of President Hyrum Smith, nephew of Joseph Smith and sixth President of the Church
“The great and glorious principle of plural marriage was first revealed to Joseph Smith in 1831, but being forbidden to make it public, or to teach it as a doctrine of the Gospel at that time, he confided the facts to only a very few of his intimate associates.” (Deseret News, May 20, 1886, Andrew Jenson, The Historical Record 6 [Salt Lake City, Utah, May 1887]: 219)
Helen Mar Kimball, plural wife of the Prophet Joseph Smith
“The Lord revealed it [plural marriage] to His prophet, Joseph Smith, as early as the year 1831.” (Whitney, Helen Mar Kimball Smith. Why We Practice Plural Marriage. Salt Lake City: Juvenile Instructor Office, 1884, pg. 53.)
Lucy Walker, plural wife of the Prophet Joseph Smith
Plural marriage “was revealed to the prophet in ‘31, but he did not teach it then … he received a revelation on polygamy in 1831.” (Kimball, Lucy Walker Smith. Testimony in the Temple Lot Case, part 3, page 450–51, questions 27, 53)
An early pioneer, a participant in Zion’s Camp and member of the First Quorum of the Seventy, Joseph B. Noble stated that the revelation on plural marriage was given during Joseph Smith’s translation of the Bible.
“That the Prophet Joseph told him that the doctrine of celestial marriage was revealed to him while he was engaged on the work of translation of the scriptures, but when the communication was first made the Lord stated that the time for the practice of that principle had not arrived.” (Noble, Joseph B. Centerville, Davis Co, Utah Stake conference, June 11, 1883. Quoted in Andrew Jenson, “Plural Marriage,” Historical Record 6 (July 1887): 232–33.)
The revelation on plural marriage, D&C 132, indicates that this further light and knowledge came after the Prophet inquired regarding the polygamous marriages of Abraham, Isaac, Jacob and many other ancient prophets.
“Verily, thus saith the Lord unto you my servant Joseph, that inasmuch as you have inquired of my hand to know and understand wherein I, the Lord, justified my servants Abraham, Isaac, and Jacob, as also Moses, David and Solomon, my servants, as touching the principle and doctrine of their having many wives and concubines—” (D&C 132:1)
The Prophet Joseph Smith was engaged in translating the book of Genesis during the months of February and March 1831.