Though I'm not quite sure what happens to Polygamy, Biblically. The Patriarchs and Kings were not one-woman men. And this is never explicitly repudiated. It does seem, historically, that polygamy had become rare among the Jews--- if it had not faded out entirely --- by the Christian era.
I read articles on this a while back in the Jewish Encyclopedia online (both on Monogamy and on Polygamy) and --- if I'm remembering correctly -- over the centuries just before and just after the time of Christ (though they didn't describe the timing that way) it gradualy disappeared. There wasn't a General Council of some kind that specifically rejected it. Polygamy simply became, for most of Judaism, a moot point. Anybody have more information on that?
http://www.chabad.org/library/article_cdo/aid/558598/jewish/Does-Jewish-Law-Forbid-Polygamy.htm
The Jewish Encyclopedia is not really a Jewish source. A similar source that is Jewish is
http://www.jewishvirtuallibrary.org/index.html