Not true.
First of all, not technically in terms of the century mark:
Like I am, B. Carmon Hardy is a descendent of Lds polygamists. Hardy, in his appendix to his book, Solemn Covenant: The Mormon Polygamous Passage, lists person by person about 250 men who took on additional plural wives between 1890-1910 (post polygamy announcement).
These were quietly solemnized by Lds officials, often in Mexico.
Secondly, Lds officials didn't break up most of the already-existing polygamous unions. So some of those Hardy documented as marrying in the early 1900s were still alive in the early 1960s.
Even beyond that, Lds view afterlife as "another planet living." Hence, Lds accept polygamy when it's colonized to Kolob; but not here. That's why Lds men and women who have multiple serial spouses, and are sealed to each in the temple for eternity, will supposedly (in the Mormon worldview) make them eternal polygamists.
If this view is correct (which I don't believe it is), people alive in 2010 wpuld be eternal polygamists. (And, some Lds apostles have taught that polygamy will be re-instituted when the Mormon Jesus returns -- see Bruce McConkie's book, Mormon Doctrine).
It is sure not because GOD told them to quit the 'practice'.