May 10, 2012 -- President Barack Obama announced that he now supports legal recognition of same-sex marriage, the first sitting U.S. president in history to do so. The statement comes on the heels of a vote in North Carolina that banned state recognition of same-sex unions.

According to a Gallup poll released on May 8, half of the American public supports legal recognition of same-sex marriages with all the rights and privileges of "traditional marriage." Forty-eight percent of those surveyed oppose it.

But what exactly is a "traditional marriage" in Western society? And how has the United States treated the institution through its history?

While opponents of legal recognition of same-sex unions define marriage as strictly a partnership between one man and one woman, the real answer is more complex than that.

Photo of Mildred and Richard Loving.