(CNN) -- Vermont's House and Senate voted Tuesday to override the governor's veto of a bill legalizing same-sex marriage in the state.
Demonstrators in Iowa celebrate that state's approval of same-sex marriage on Friday.
The Senate voted 23-5 to override Gov. Jim Douglas' veto, according to the Senate office. Shortly afterward, the House overrode the veto on a 100-49 vote. The votes surpassed the number needed -- two-thirds of those present -- to override the veto.
The action makes Vermont the fourth state to legalize same-sex marriages. The others are Massachusetts, Connecticut and, as of last week, Iowa.
Douglas vetoed the bill Monday. "Vermont's civil union law has afforded the same state rights, responsibilities and benefits of marriage to same-sex couples," the governor wrote in a letter to David Gibson, secretary of the Senate. "Our civil union law serves Vermont well, and I would support congressional action to extend those benefits at the federal level to states that recognize same-sex unions. But I believe that marriage should remain between a man and a woman."
Tuesday's votes end a 10-year battle to legalize same-sex marriage in Vermont despite a court ruling legalizing civil unions, according to CNN affiliate WPTZ-TV. Same-sex marriages will become legal on September 1.
Following the House vote, corridors of the legislative building filled with jubilant supporters, some embracing and others talking on cell phones to spread the news, WPTZ said.
"We haven't decided who's going to propose to who yet," said one man, standing with his partner. The couple told WPTZ they will have been together 25 years in September.
The Human Rights Campaign, which describes itself as the nation's largest lesbian, gay, bisexual and transgender civil rights organization, issued a statement applauding the votes, noting Vermont is the first state to legalize same-sex marriage through the legislative process.
"This historic vote in the Vermont Legislature reminds us of the incredible progress being made toward equality," said Joe Solmonese, Human Rights Campaign president, in the statement. "Less than five years ago, lesbian and gay couples began marrying in Massachusetts. Now, with the Iowa court decision last Friday and today's vote in Vermont, there will be four states recognizing the right to marry for loving, committed lesbian and gay couples."
Vermont Senate President Pro Tem Peter Shumlin was quoted in the statement as saying, "The struggle for equal rights is never easy. I was proud to be president of the Senate nine years ago when Vermont created civil unions. Today we have overridden the governor's veto. I have never felt more proud of Vermont as we become the first state in the country to enact marriage equality, not as the result of a court order, but because it is the right thing to do."
Vermont's neighboring state, New Hampshire, also has taken steps toward legalizing same-sex marriages. On March 26, the New Hampshire House passed a bill by seven votes that would legalize same-sex marriage, sending it to the Senate, according to the Concord Monitor newspaper.
New Hampshire Gov. John Lynch has said he opposes same-sex marriage but has not said whether he will veto a bill legalizing it. Like Vermont, New Hampshire allows civil unions for same-sex couples.
"The civil unions bill [Lynch] signed into law prevents discrimination and provides the same legal protections to all New Hampshire families to the extent that is possible under federal law," Lynch spokesman Colin Manning told the Monitor.
On Friday, the Iowa Supreme Court struck down a state law banning same-sex marriage. The decision upheld a 2007 ruling by a lower court that struck down Iowa's 1998 law limiting marriage to heterosexual couples.
Polk County District Judge Robert Hanson found that the law violated the state constitution's guarantee of equal protection and hurt gay and lesbian couples "in numerous tangible and intangible" ways.