But it's unclear how popular beliefs will evolve in the places where the future of same-sex marriage is now being decided. In 2004, 75 percent of Arkansans voted for a constitutional amendment that stated that "marriage consists only of the union of one man and one woman." A decade later, clerks in counties across the state are issuing marriage licenses to gay women and men.

Legislative Action for and Against Same-Sex Marriage

In the coming months, similar rulings may make same-sex marriage legal in many of other states that passed constitutional bans with strong majorities. More than three-quarters of Oklahomans voted for an amendment to outlaw gay unions in 2004; a ruling against that law is awaiting appeal. The same is true of Texas, where 76 percent of its residents voted for a similar amendment in 2005. Next month, oral arguments will be heard in a challenge to Louisiana's ban, which nearly 80 percent of residents voted for in 2004; many other case developments are expected in throughout the summer and early fall.

U.S. Court Cases on Same-Sex Marriage

Pew Research Center

A lot has changed in the last decade—and not just in terms of legal status. In Pew surveys of nationwide attitudes toward same-sex marriage in 2012 and 2013, researchers found that many people had changed their minds over the course of 10 years. The graphic at right, for example, shows just how much perspectives have shifted: Last year, 60 percent of people said "homosexuality should be accepted by society," up from 47 percent in 2003. And the percentage of people who said they have a "favorable opinion" of gays and lesbians was up by 16 and 19 percentage points, respectively.

But even though Americans have clearly become more comfortable with homosexuality, the 2013 poll numbers indicate significant ambivalence. A majority of people still say that same-sex marriage goes against their religious beliefs. Forty-five percent of people believe it is a sin to participate in "homosexual behavior." Forty percent would be upset if their child were gay or lesbian, and perhaps most tellingly, only slightly more than half of people say they have a favorable opinion of gay men.

Pew Research Center

These views vary a lot by region. This geographic breakdown of attitudes toward the LGBT community from 2012 is slightly dated, but it gives a good sense of the places where people are most uncomfortable with homosexuality.