Lets get our history right.....
I contend that polygamy was never legal in this country. If I'm wrong you can enlighten me....
The Mormons of Utah were practicing polygamy while Utah was a territory, and Lincoln took care of that in 1862....
In no state of the US was it ever legal that I'm aware of....
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http://www.xmission.com/~plporter/lds/chron.htm
1862 July 8, Morrill Anti-Bigamy Law, signed by Abraham Lincoln.
* First basic federal legislation by the Congress of the United States that was designed "to punish and prevent the practice of polygamy in the Territories of the United States".
* Bigamy punishable by a $500 fine and imprisonment not exceeding five years.
* All acts passed by the Legislative Assembly of the Territory of Utah "pertaining to polygamy and spiritual marriage" were annulled.
1879 January 6, in the first constitutional challenge to interpret the First Amendment to the Constitution, the United States Supreme Court upheld the decision of the territorial court and declared that every civil government had the right to determine whether monogamy or polygamy should be the law of social life under its jurisdiction.
* Thus the Morrill act of 1862 was declared valid, any additional plural marriages were clearly breaking the law of the land. (Larson, pp. 78-79.)
Utah didn't even become a state until 1896.