The D.C. City Council voted 11-2 in favor of same-sex marriage Tuesday morning.
It was the first of two votes on the issue allowing same-sex marriage in the nation's capital.
The bill sponsored by openly gay Councilman David Catania had been expected to pass for some time, as 10 of the 13 council members supported its introduction. Only Councilman Marion Barry and Councilwoman Yvette Alexander voted against it Tuesday.
The final vote is expected later this month, and Mayor Adrian Fenty has said he will sign the bill.
Same-sex marriages would begin in the city as soon as the bill passes a period of Congressional review. Congress is not expected to alter the law.
Earlier this year, the council set the table for this bill when it passed a bill recognizing same-sex marriages performed in other states. Opponents fought and failed to have that bill put to a vote by the people in 2010.
The Archdiocese of Washington has threatened to withdraw millions in funding for D.C. social services to the poor and homeless if gay marriage is legalized in D.C.
The Catholic Church wants to be exempted from having to pay spousal benefits to any gay employees -- as the church doesn't recognize gay marriage -- and wants to avoid being forced to handle gay adoptions.
Both Catania and Councilman Phil Mendelson said the church should use the same policy as Georgetown University -- a Jesuit organization that does not officially recognize gay marriage but provides spouse-like benefits to its adult employees. A similar law allows such arrangements in San Francisco.
Massachusetts, Iowa, Vermont and Connecticut already allow same-sex marriage. New Hampshire will join them Jan. 1.