Q&A: Same-sex marriage in the US
Support for gay marriage in the US has gained momentum since the US Supreme Court delivered victories to supporters in two landmark rulings in June.
Since then, several states have approved same-sex nuptials by legislation or through court cases. Other states have cases pending.
So, what does it all mean and how did we get to this point?
How many US states allow same-sex marriage?
Gay weddings are currently legal in 15 states: California Connecticut, Delaware, Illinois, Iowa, Maine, New Jersey, Maryland, Massachusetts, Minnesota, New Hampshire, New York, Rhode Island, Vermont, Washington state, as well as in Washington DC.
In Hawaii, a bill legalising gay marriage awaits a governor's signature to become law.
What about states where it is banned?
The remaining 34 states do not legally sanction gay marriage, but laws vary greatly. Some states have civil union laws that grant couples most if not all of the rights and benefits of marriage.
Other states have passed bans or state constitutional amendments forbidding such unions. Others, like Oregon, ban same-sex marriage but recognise couples married in other states.
Some counties in the state of New Mexico, which has no law either way on the issue, began issuing marriage licences to gay couples in August and September. A court case sent to the New Mexico Supreme Court is expected to resolve the issue for the entire state.
Why was this issue considered by the Supreme Court?
Describing marriage as a civil-rights issue, advocates said that the US should not have a two-tiered system in which some people may marry - and receive the financial benefits that come with being married - while others may not, while others argued it should be determined by each US state.
Opponents of same-sex marriage adhered to what they call the traditional definition of marriage - between a man and a woman - and said the government should not redefine that.
The recognition of gay unions by some states, but not the federal government, created a legal conundrum that allowed advocates to bring the issue to the top court in the US.
The first case before the Supreme Court, United States v Windsor, was a challenge to the Defense of Marriage Act (Doma), passed by Congress in 1996. Under this law, same-sex marriages approved at the state level were not recognised by the federal government.
This meant, for example, that individuals in same-sex marriages were ineligible for benefits from federal programmes such as the Social Security pension system if their partners died.
Edith Windsor, an 83-year-old widow, said it was unfair that she was required to pay $363,000 (£239,000) in extra taxes after her wife's death, simply because she was a woman.
The other case, Hollingsworth v Perry, was filed by two lawyers, Theodore Olson and David Boies, working together on behalf of their California clients, Kristin Perry and Sandra Stier and another couple, Jeffrey Zarrillo and Paul Katami.
They argued that the Supreme Court should strike down a state law, called Proposition 8, which stated that marriage is between a man and a woman. The law, approved by California voters in 2008, overrode a state Supreme Court decision that allowed for same-sex marriage.
What does the ruling on Doma mean?
The Doma decision means that legally married gay men and women are entitled to claim the same federal benefits available to opposite-sex married couples.
These cover areas like tax, social security and immigration.
The challenge to Doma did not address the question of whether same-sex marriage is constitutional.
What about Prop 8?
The decision, which effectively legalised gay marriage in California, was decided on technical grounds when the majority of judges, 5 to 4, decided the case was not properly before the court.
Supporters of Proposition 8, they ruled, were not entitled to appeal the decision by another court in California to strike down the ban.
So, the Supreme Court left in place the victory by the state court for two same-sex couples who had sought to marry.