The data visualization wizards at the Los Angeles Times put together a great chronological map that illustrates the change in same-sex marriage rights by state since 2000. Click the image below to see the interactive version.
In 1996 the U.S. Congress passed the Defense of Marriage Act (DOMA), stating that "the word ‘marriage’ means only a legal union between one man and one woman as husband and wife, and the word ‘spouse’ refers only to a person of the opposite sex who is a husband or a wife.’’.
Under the federal law, states do not have any obligation to recognize same-sex marriages and the legal/financial rights that go along with it. However, individual states have the power to decide - either through legislation or voter initiative - to legalize same-sex marriages. And in recent years, a growing number of states have done just that. They include Massachusetts, New York, Connecticut, Iowa, Vermont and New Hampshire, as well as Washington D.C. In the 2012 election, voters in the state of Washington, Maryland and Maine also legalized marriage for same-sex couples, raising the total number of states to nine.
In California, same-sex marriage was briefly allowed until voters in 2008 passed Proposition 8, which struck down the law. A federal court has since ruled Prop 8 unconstitutional. Same-sex marriages, however, have yet to resume here, and the U.S. Supreme Court is now considering whether to hear the case.