Updated Feb. 15, 2013

On Feb. 14, the Illinois Senate, as expected, approved a measure that would legalize same-sex marriage in the state. The bill will move next to the Illinois House of Representatives, which is more divided on the issue. Illinois Gov. Pat Quinn favors the legislation and has said he will sign it if it reaches his desk. Nine states and the District of Columbia already allow gays and lesbians to marry. (See Graphic: Same-Sex Marriage State-by-State.)

Since Massachusetts became the first state to legalize gay marriage a decade ago, the debate over whether to allow gays and lesbians to wed has spread to state legislatures, courts and ballot initiatives across the country. This year is no exception. In addition to Illinois, Rhode Island now is weighing the issue. Legislation legalizing gay marriage won the approval of Rhode Island’s House of Representatives on Jan. 24 and will be taken up by the state Senate next, though no timeline has been set.

In early March, the U.S. Supreme Court is scheduled to hear two same-sex marriage cases. Meanwhile, the issue also is rising internationally; 11 countries have legalized gay marriage since 2000, and two more – France and Great Britain – are poised to do so later this year.

All of this comes at a time when support for same-sex marriage has been on the rise. In 2001, 57% of Americans opposed gay marriage, while just 35% supported it. A decade later, in 2011, the public was about evenly divided, with 46% supporting gay marriage and 45% opposing it. And Pew Research polling conducted in 2012 finds slightly more support for same-sex marriage (48%) than opposition to it (43%).

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