After suffering setbacks from California to New York, Maine to New Jersey, same-sex marriage supporters got a victory Tuesday with the City Council's vote to legalize gay marriage in the District of Columbia.

Gay couples could begin tying the knot in the district as early as March. The only hurdles left to clear are the city's mayor, who has promised to sign the bill, and Congress, which has final say over laws in the nation's capital. The district's nonvoting delegate to Congress, Eleanor Holmes Norton, said she expects no opposition there.

"Make no mistake, 2009 has been one hell of a year for marriage equality," said David Catania, who introduced the bill and is one of two openly gay council members.

Council members said that it was symbolic that the nation's capital had voted to pass gay marriage. But the city is also in many ways not representative of the nation. More than three quarters of the voters in the city of 600,000 are registered Democrats.

Patrick J. Egan, a professor of politics at New York University, called the city "the most liberal and Democratic-party-dominated jurisdiction in the United States."

Congress now has 30 working days to act on the bill, but it has rejected legislation just three times in the past 25 years.

"I believe I have assurances that the barn door is locked," said Norton, a Democrat who called the legislation "historic" and said she was "proud" of the council.

Tuesday's 11-2 vote was no surprise. Two members voted "I do" when their names came up, and when the vote finished a packed chamber erupted into cheers and applause. The "no" votes included former Mayor Marion Barry, now a council member.

If the bill becomes law, the district will join Connecticut, Iowa, Massachusetts and Vermont in issuing marriage licenses to same-sex couples. They will be able to wed in New Hampshire starting in January.

Gay marriage supporters have had less success elsewhere recently. Maine voters overturned the state's same-sex marriage law last month. Earlier this month, the New York state Senate rejected a bill that would have allowed gay couples to marry.

The New Jersey Legislature, which had been working on a same-sex marriage bill, postponed a recent vote when the measure appeared headed for defeat. Sponsors now want the Assembly to consider it first, but that probably won't happen until after the new year, if at all.

Tuesday's vote in the district came after several months of discussion, including two marathon council hearings at which some 250 witnesses testified.