The California Assembly voted Tuesday to allow gay and lesbian couples to marry, becoming the first legislative body in the US to approve same-sex marriages.
The state Assembly, which is controlled by Democrats, passed the Religious Freedom and Civil Marriage Protection Act by a vote of 41 to 35, which recasts the definition of marriage as between "two persons," not between a man and a woman.
The bill passed the state's Senate last week in a 21-15 vote.
The bill's supporters compared the legislation to earlier civil rights campaigns, including efforts to eradicate slavery and give women the right to vote.
Democratic Assemblyman Paul Koretz called bans on gay marriage "the last frontier of bigotry and discrimination, and it's time we put an end to it."
But opponents repeatedly cited the public's vote five years ago to approve Proposition 22, an initiative put on the ballot by gay marriage opponents to keep California from recognising same-sex marriages performed in other states or countries.
"History will record that you betrayed your constituents and their moral and ethical values," said Republican Assemblyman Jay La Suer.
California already gives same-sex couples many of the rights and duties of marriage if they register with the state as domestic partners.