When a practice becomes intrenched in a community, it can take time to convince people that it should end. This was the case among Latter-day Saints when Wilford Woodruff received the revelation ending the practice of polygamy. Many in the membership of the Church resisted this change in practice. So, they looked for ways around the declaration ending the practice (the Manifesto). One way to get around it was to solemnize marriages outside of the United States, in countries where such marriages were not illegal. Because of this, Joseph F. Smith (nephew of Joseph Smith and then President of the Church) issued the "Second Manifesto" (http://en.wikipedia.org/wiki/Second_Manifesto) in the General Conference held 6 April 1904. This declared that polygamous marriages created after the Manifesto was issued were not sanctioned by the Church and that anyone one solemnizing and/or entering into a new polygamous marriage after this time could face excommunication. As a result of this, a number of Church officers were disciplined. These included two apostles who were removed from that quorum for their opposition to this change. One of these former apostles, John W. Taylor (the son of the third President of the Church, John Taylor) was eventually excommunicated. The enforcement of this ban on polygamy was probably one of the biggest catalysts for the formation of the Fundamentalist LDS movement.

D & C 132 it is still in your scriptures, wheather it be in the spirit world or not, it is still there.

SHORT ANSWER: 1904 LONG ANSWER: From D. Michael Quinn: "In 1968, a Sunday School manual stated, "A few were married after 1890 in Mexico, Canada and the high seas-outside the jurisdiction of the United States. It was not until 1904, under the leadership of President Joseph F. Smith, that plural marriage was banned finally and completely, everywhere in the world, by the Church." ("LDS Church Authority and New Plural Marriages, 1890—1904"; Dialogue: A Journal of Mormon Thought, Spring 1985)