The Vermont Legislature has only overridden a governor's veto six times in its history. (The last was 19 years ago.) The vote for same-sex marriage the previous week was five votes short of the necessary supermajority. Shap Smith, the boyish-looking state representative from a working-class town who had become Speaker of the House just three months earlier, had been working the phones to persuade reluctant colleagues to override. He was taking on a popular four-term Republican governor who had regularly outmaneuvered the Democratic legislature. By this morning, everyone knew the final vote would be razor thin; no one could confidently predict the outcome.

In the mundane rituals that belie the historic significance of the moment, the roll of the House was called by the clerk as it has been since the American Revolution, one by one. One hundred and forty-nine times (one legislator was out sick), a name rang out, and was greeted with a "yes" or "no." As the last of the names was called, a swell of murmurs rippled through the galley. Finally, Speaker Smith, his voice cracking with emotion, announced, "Those voting yes, a hundred. Those voting no, 49. A hundred needed to pass; you have voted to override the veto."

A swing of the gavel, an explosion of emotion from spectators in the galley and from members of the legislature who rose to their feet to clap, and same-sex marriage was legal in Vermont. It's the fourth state in the country to allow same-sex marriage—Massachusetts, Connecticut, and Iowa legalized it as a result of court orders—and the first in the country to do so through a vote of its elected leaders.

As I walked up the long, grassy lawn in front of the Vermont State House on the chilly, wet morning of the historic override vote, I had a sense of déjà vu. Large signs stood in front of the gold-domed building. "Believe in Our Common Humanity." "Override for Love." A lone "Take Back Vermont" sign, the slogan of gay-marriage opponents, stuck in the soft, wet spring earth.

Nine years ago, I covered the battle for civil unions in Vermont for Mother Jones. In 1999, the Vermont Supreme Court ruled in Baker v. Vermont that gay and lesbian couples were entitled to the same legal rights and benefits of marriage as heterosexual couples. The court ordered the Vermont legislature to craft a law that would satisfy the ruling, either by legalizing gay marriage or by creating an equivalent partnership structure. The decision, wrote Chief Justice Jeffrey Amestoy, "is simply a recognition of our common humanity." In April 2000, the Vermont legislature passed civil unions, the legal equivalent of heterosexual marriage. Gov. Howard Dean signed it into law the next day.

That winter of 2000, the debate over civil unions raged for four months. I vividly remember arriving at the State House in the midst of a blizzard for the public hearings. Inside, thousands of Vermonters in down jackets and snow boots were camped out in the halls and in the chamber of the House of Representatives. Opponents of civil unions warned that God’s wrath would come down upon the state if "the homosexual agenda" was enacted. Southern Christian churches bused in activists to oppose the effort. But Vermont political leaders barred out-of-state residents from speaking, ensuring that the discussion over gay rights would take place among neighbors. I witnessed one result of this when I came across fanatical anti-abortion leader Randall Terry, founder of Operation Rescue, reduced to shouting himself hoarse on the windswept and icy steps of the State House, unable to make his case to the legislators inside.

This time, the debate was different. For starters, the sky hasn't fallen in the nine years that Vermont has allowed same-sex unions. Gay and lesbian couples have had civil unions, raised kids, and some have divorced, just like straight couples. A cottage industry for civil unions has flourished in the state. A recent study of the economic impact of legalizing same-sex marriage in Vermont projected that it would boost the economy by more than $30 million, generate $3 million in local taxes and fees, and create about 700 new jobs. For a cash-strapped state whose governor recently proposed reducing the state work force by roughly the same number of jobs, it was another compelling argument.

The Vermont Legislature held a public hearing about gay marriage on March 18. There was no blizzard this time. Thousands of Vermonters came to the State House, and the event was notably civil. Marriage supporters wore bright yellow buttons that declared, "From Legal Rights to Equal Rights." Opponents sported white stickers that stated, "Marriage: A mother and father for every child." The opponents' choice of slogan was telling: With roughly half of heterosexual marriages ending in divorce, their rallying cry seemed to be more nostalgia for a bygone era than about the ragged reality of modern family life.

Outside the chamber, I spoke with William Moore, a carpenter from Cambridge, Vermont. "As a Christian man, the word 'marriage' is defined by God," he told me. "They are seeking to co-opt the word and redefine it. They are going to strip all meaning from the word for their political desires. It's not a civil rights issue." I then asked him what he thought about civil unions. "I don't have a problem with civil unions," he replied quickly. "It doesn't dilute or add to the institution of marriage in any way."

It was a sentiment I heard often: Civil unions are passé. Even President George W. Bush offered his endorsement in the 2004 election campaign, contradicting the Republican Party platform when he declared, "I don't think we should deny people the right to a civil union."

Beth Robinson, the attorney who filed the original Baker lawsuit and the board chair of the Vermont Freedom to Marry Task Force and Action Committee, told me in the crush of the State House halls that marriage provides protections that civil unions cannot. Other states recognize marriage, but they do not recognize civil unions, leaving gay and lesbian couples and families without legal rights outside the state. "Same-sex marriage won't erase the problems between the states, but it will erase some of the barriers," she said. Some of the marriage benefits include Social Security survivor benefits and access to a partner's health insurance.

Then there is the matter of dignity, which gay and lesbian families addressed inside the House chamber. The most memorable testimony came from children. Evann Orleck-Jetter, a 12-year-old girl with shoulder-length black hair from Thetford Center, strode confidently to the microphone. Speaking of her two moms, she said, "I love them very much and I wish that having to stand up here right now in front of this committee wasn't an issue anymore. We should be past this." She continued, "It hurts me sometimes when I feel invisible, because few people understand my feelings about my family, and few people want to ask about families with two moms...It's time to accept and honor families like mine. Passing this law will make it easier for me talk about my family openly, and the subject won’t have to stay behind closed doors. This would mean so much to me, my brother, and many others." When she rose and walked back to her seat, I looked around at the legislators who were listening. Many were dabbing their eyes. Several lawmakers told me later that night that the testimony from Evann, and also from 13-year-old Irene Shamas from Putney, Vermont, affected them deeply and would influence their vote.

On the day of the veto override, I talked to Evann's mom, Alexis Jetter. "Nine years ago, I came here and testified with my 3-year-old daughter on my lap. Now, to have her testify alongside me, to have people tell her that she changed history—it's an amazing experience."

The 51-year-old lesbian mother, visibly moved, added proudly that Evann was "a model for how people can stand up. We face bigotry and intolerance. You can't change the haters. But you can talk to them."

The victory of same-sex marriage in Vermont was the culmination of a dozen years of organizing. The Vermont Freedom to Marry Task Force was established in 1996 largely to file the original lawsuit that resulted in civil unions. That episode was politically costly: Civil unions won, but a number of state lawmakers who voted in favor of it were targeted and defeated in the 2000 election, turning control of the Vermont House of Representatives to Republicans. It took Democrats four years to win back a majority of House seats.

In 2008, Vermont Freedom to Marry announced its intention to push the Legislature for full marriage equality. This time, Democratic leaders promised to take up the matter in 2009, after elections. Activists spent the year organizing, lobbying, and holding house meetings around the state. On the night of the public hearings in March, a long line of buses arrived at the State House from around Vermont bearing gay-marriage supporters who came in an organized show of force.

Opponents were also organized, but they made a critical last-minute error. The week before the vote, the National Organization for Marriage robocalled thousands of Vermonters urging them to oppose same-sex marriage. I received one of the calls, and it urged me to call, well, my wife, who is a Vermont state representative. Within minutes, my phone began ringing nonstop. The next morning, we checked our voicemail: Out of more than a dozen calls we received, all but one urged her to vote in favor of gay marriage. Numerous callers expressed outrage that out-of-state groups were trying to influence the debate. Charges of outside meddling have long been the kiss of death in this proudly self-reliant Yankee state.

For Republican Gov. Jim Douglas, the battle represented a serious political miscalculation. Even the top Republican leaders in the House of Representatives voted to override his veto. He was playing to a conservative base, but failed to grasp that the goal lines around this issue have moved significantly. In house meetings and public forums, gay and lesbian Vermonters and their kids took the risk of reaching out to their neighbors to make their case. And their neighbors listened.

"We're thrilled to be the first state to open up the legislative arena as a viable option to achieving equality, and we look forward to supporting our sister states around the country," attorney Beth Robinson told me after the veto override. Among the states where gay marriage is gaining legislative support are New York, New Jersey, Maine, and New Hampshire. Nationally, the picture is more bleak: 30 states have passed some type of constitutional bans on same-sex marriage. But what happened in Vermont signals that the anti-marriage movement has sparked a backlash. Several Vermont legislators told me that the recent passage of Proposition 8 in California, which amends the state constitution to ban same-sex marriage, emboldened them to legalize marriage.

In Vermont, the historic vote was an affirmation. "Today, love won," said a jubilant Jason Lorber, a gay state representative.

Rep. Bill Lippert, a gay man who is chair of the House Judiciary Committee and led the legislative fights both for civil unions and for gay marriage, beamed and welled with tears as he addressed his colleagues following the vote. "We are your neighbors. And you recognized that we are essential members of our communities." His voice breaking, he added, "If people only understood the deep love we have in our relationships, there wouldn’t have been any 'no' votes."

David Goodman is a contributing writer for Mother Jones. He is the author most recently (with Amy Goodman) of the New York Times best-seller Standing Up to the Madness: Ordinary Heroes in Extraordinary Times (Hyperion), which has just come out in paperback.