(Reuters) - The following is a look at laws on gay marriage and same-sex civil unions in the United States:
* Massachusetts' highest court ruled in 2003 that a ban on gay marriage was unconstitutional, paving the way for America's first same-sex marriages the following year.
* Connecticut's Supreme Court overturned a ban on same-sex marriage on October 10. Local authorities began issuing marriage licenses on November 12, making it the second U.S. state to allow gay and lesbian couples to marry after Massachusetts.
* California began marrying gay and lesbian couples in June 2008, a month after the state Supreme Court ruled that barring same-sex marriages was unconstitutional. But that was reversed on November 4 when Californians voted in support of a proposition to amend the state constitution to ban same-sex marriage.
* New Hampshire, New Jersey and Vermont permit same-sex civil unions that grant largely the same state rights as married couples -- from insurance coverage to tax benefits and hospital visiting rights -- but lack the full legal protections of marriage.
* Maine, the District of Columbia, Hawaii and Washington each offer gay couples some legal rights as partners.
* Forty-four states have laws explicitly prohibiting same-sex marriage, including 29 with constitutional amendments restricting marriage to one man and one woman.
* The patchwork of laws has caused some unusual complications. Rhode Island's top court, for example, ruled in December 2007 that a same-sex couple married in Massachusetts could not legally divorce in Rhode Island, saying the state's family court did not have authority over same-sex marriages.
* The U.S. Supreme Court has not taken a case on gay marriage, leaving states to decide the issue.
Compiled by Jason Szep in Boston