The U.S. Supreme Court on Wednesday let stand a lower-court ruling throwing out California's voter-approved ban on gay marriage, while also striking down a core element of a federal law that denied benefits to same-sex married couples.
Before the rulings, 12 of the 50 U.S. states allowed same-sex marriage. California would become the 13th state.
The first three states to allow gay marriage did so because of court rulings permitting it, rather than through legislative action or putting the issue to voters to decide. Since mid-2009, six states have approved gay marriage laws by passing laws in state legislatures and three states by ballot initiatives.
Here is a look at the states that have approved gay marriage.
* MASSACHUSETTS - In 2003, Massachusetts became the first state to allow gay marriage after its highest court ruled the state's ban violated the constitutional rights of same-sex couples.
* CONNECTICUT - In 2008, the state Supreme Court overturned a lower court ruling and found that same-sex couples had a constitutional right to marry. Soon after, the state began issuing marriage licenses to same-sex couples.
* IOWA - A unanimous ruling by the state Supreme Court in 2009 legalized same-sex marriage. The next year, a recall campaign by opponents of same-sex marriage forced three judges from the bench. A 2012 effort to oust a fourth judge was unsuccessful.
* CALIFORNIA - In California, the most populous state, same-sex marriage was legal briefly in 2008 following a court ruling permitting it. Later that year, voters approved Proposition 8, which banned gay marriage. The U.S. Supreme Court in 2013 decided that a lower-court ruling that struck down Proposition 8 will remain intact.
* VERMONT - In 2009, Vermont became the first state to legalize gay marriage by legislative means. Vermont in 2000 had become the first state to allow civil unions for gay couples. After the state legislature passed the measure, Governor Jim Douglas vetoed it. Legislators then voted to override his veto.
* NEW HAMPSHIRE - Two years after New Hampshire began allowing same-sex couples to enter into civil unions, the state approved gay marriage in 2009.
* WASHINGTON, D.C. - In 2009, lawmakers in the U.S. capital voted to legalize gay marriage. Because the District of Columbia is not a state, the legislation required congressional approval. In early 2010, efforts to block the law were unsuccessful and it took effect that March.
* NEW YORK - After a gay marriage bill failed in New York's Democratic-controlled Senate by a margin of 38 to 24 in 2009, advocates retooled their strategy and applied pressure to lawmakers who had voted "no." In 2011, the Republican-controlled state Senate joined the Democratic-led state Assembly and passed the bill by four votes.
* RHODE ISLAND - In 2013, after the state legislature and governor approved a gay marriage bill, Rhode Island became the last of the New England states to legalize same-sex marriage. The law takes effect on August 1.
* DELAWARE - In 2013, the Delaware state legislature approved same-sex marriage and the bill was signed into law by the governor. The law takes effect on July 1.
* MINNESOTA: 2013 - After Minnesota voters became the first to reject a proposed state constitutional amendment defining marriage as a union between a man and a woman in 2012, the state legislature proposed a same-sex marriage legalization bill in 2013. The bill was approved and takes effect on August 1.
* MAINE - When supporters of same-sex marriage put the issue on the ballot in Maine, it marked the first attempt to legalize same-sex marriage in a popular referendum. It was approved by voters in the November 2012 elections.
* MARYLAND, WASHINGTON STATE - After the state legislatures in Washington and Maryland voted in favor of same-sex marriage, the laws were blocked from taking effect until state voters were given an opportunity to decide the matter in ballot initiatives. The issue went to voters in November 2012 and in both states voters sided with legalizing same-sex marriage.
(Reporting by Edith Honan; Editing by Howard Goller and Will Dunham)