The Beginnings of Polygamy
1830 The first edition of the Book of Mormon directly taught against polygamy (plural marriage) calling it "abominable" and being "not right with the Lord". (See Jacob 2:24, 27-28; Jacob 3:5; Mosiah 11:2; Ether 10:5...all quotes from the Book of Mormon)
"And now it came to pass that the people of Nephi, under the reign of the second king, began to grow hard in their hearts, and indulge themselves somewhat in wicked practices, such as like unto David of old desiring many wives and concubines, and also Solomon, his son." (Jacob 1:15)

"Behold, David and Solomon truly had many wives and concubines, which thing was abominable before me, saith the Lord." (Jacob 2:24, Book of Mormon)

"Wherefore, my brethren, hear me, and hearken to the word of the Lord: For there shall not any man among you have save it be one wife; and concubines he shall have none; for I, the Lord God, delight in the chastity of women. And whoredoms are an abomination before me; thus saith the Lord of Hosts." (Jacob 2:27-28, Book of Mormon)

"Behold, the Lamanites your brethren, whom ye hate because of their filthiness and the cursing which hath come upon their skins, are more righteous than you; for they have not forgotten the commandment of the Lord, which was given unto our father—that they should have save it were one wife, and concubines they should have none, and there should not be whoredoms committed among them. And now, this commandment they observe to keep; wherefore, because of this observance, in keeping this commandment, the Lord God will not destroy them, but will be merciful unto them; and one day they shall become a blessed people." (Jacob 3:5-6, Book of Mormon)

"And it came to pass that Riplakish did not do that which was right in the sight of the Lord, for he did have many wives and concubines, and did lay that upon men’s shoulders which was grievous to be borne.... (Ether 10:5, Book of Mormon)

1831 Joseph Smith wrote the following which appeared on page 91 of the Book of Commandments: "Thou shalt love thy wife with all thy heart, and shall cleave unto her and none else." But later that year (revealed by Joseph Smith in 1831 but not written down until 1861 in a letter from W.W. Phelps to Brigham Young), on July 17th, Joseph Smith gave the following permission/revelation, "...For it is my will that in time, ye should take unto you wives of the Lamanites and Nephites, that their posterity may become white, delightsome and just, for even now their females are more virtuous than the gentiles."
1834 Revealed in the same letter from W.W. Phelps to Brigham Young written in 1861 (see 1831) , W.W. Phelps disclosed the following revelation from Joseph Smith which dates to approximately 1834, "...I asked brother Joseph, privately, how "we" that were mentioned in the revelation could take wives from the "natives" as we were all married men? He replied, instantly "In the same manner that Abraham took Hagar and Keturah; and Jacob took Rachel, Bilhah and Zilpah; by revelation -- the saints of the Lord are always directed by revelation.""
1835 Polygamy began to be practised "in private" by Joseph Smith around this time, while still being publicly denounced right through 1844. The Mormon church denied the practise of polygamy in the 1835 edition of the Doctrine & Covenants but it was removed from the Doctrine & Covenants (D&C) in 1876 when the doctrine of "plural marriage" (polygamy) was inserted in D&C Section 132.
"Inasmuch as this church of Christ has been reproached with the crime of fornication, and polygamy: we declare that we believe, that one man should have one wife, and one woman, but one husband, except in the case of death, when either is at liberty to marry again." (1835 edition of the Doctrine and Covenants, Section 101:4)
1840 "In 1840 the doctrine [polygamy] was taught to a few leading brethren who, with the Prophet, secretly married additional wives in the following year..." (The Restored Church, pg. 247)
1843 Joseph Smith allegedly received instruction ("revelation") from God that permitted polygamy to be practiced. (This revelation is Section 132 of the Doctrine and Covenants) Of course, this revelation was kept quiet and shared with Emma, Smith to keep her in line, and several other "inner circle" leaders (who also began to practice polygamy). Polygamy was not announced to the Church as a whole until 1852. It was not committed to print 1876. It was finally voted on in 1880, just ten years before Mormonism was forced to publicly renounce the sealing of plural marriages. Of course, the Church did not end polygamy at that time, but sent polygamists to the deserts of Utah and to Mexico.
1844 On Feb. 1st, Joseph Smith allegedly excomunicated Hiram Brown, an elder of the Mormon church for "preaching" polygamy. (Times and Seasons, vol. 5, page 423)

William Law (publisher of "The Nauvoo Expositor") published in his newspaper on June 7th the practise of plural marriage (polygamy) in Nauvoo and Joseph Smith's teachings on multiple gods.

Joseph Smith was so enraged that he ordered the destruction on June 10th of "The Nauvoo Expositor".

On June 25th, Joseph Smith was arrested for and charged with "riot" for the destruction of the newspaper office and he was thrown in the Carthage, Illinois, jail where he was murdered by an angry mob on June 27th.

1852 The practice/doctrine of plural marriage (polygamy) is officially announced on August 28-29th at a public Mormon meeting.