When the clock struck 12 they made history as the city hall clerks threw open the doors to more than 260 same-sex couples to fill out marriage licence forms, making Massachusetts the first state in the US to legally sanction same-sex marriages.

Marcia Hams and Susan Shepherd were first in line, having queued all day on Sunday. They had had 27 years of being together to imagine the moment, but when it came it still took them by surprise. "This is amazing," Ms Shepherd said. "You never thought this would ever happen, not in any amount of lifetimes you could think about. There's a kid somewhere watching this. It's going to change his whole life."

Most of the crowd, which included many heterosexual people, had come to cheer them on. Bob and Don, who have been together for 29 years, had been there since 8pm. "We just came to support the whole thing," said Bob, who was not sure if they would marry. "The institution certainly has its problems. But what's important is that now we have the choice."

An anti-gay backlash had been feared but did not materialise on the night, although a handful of protesters, some of whom had travelled from as far as Kansas, carried banners declaring "God hates fags" and made their views known in the cordoned-off "first amendment zone".

"If they're going to allow this, then why not incest?" asked Ben Phelps of Topeka, Kansas. "Why not have people marry animals? Why not polygamy?"

But for the most part it was a night of celebration which carried on into the early hours as dawn saw couples race to be first in line outside city halls across the state. By law, couples should wait three days between getting their licence and getting married. But in many areas the courts yesterday issued waivers for those who did not wish to wait.

Cambridge, once again, was first, declaring Marcia Kadish, 56, and Tanya McCloskey, 52, who have been partners for 18 years, wife and wife.

"Now by the power vested in me by the state of Massachusetts as a justice of the peace, and most of all by the power of your own love, I now pronounce you married under the laws of Massachusetts," said Margaret Drury, a city clerk. "You may seal this marriage with a kiss." The couple embraced.

Massachusetts joins the Netherlands, Belgium and Canada's three most populous provinces as one of the few places in the world where gay marriages are recognised.

The prospect of wedding bells chiming also set cash tills ringing, as businesses sought to make the most of a market which, according to Forbes magazine, could be worth around $16.8bn (£9.5bn). Hers-and-hers towels, his-and-his tuxedos and two brides or grooms for the top of wedding cakes are just a few of the items increasingly available.

"Everybody knows this is where the money is, because gays generally have more disposable income," Nancy Levy, the co-owner of the event planning firm Weddingtown USA, told USA Today.

"I talked to one of my vendors - very Republican, wears Bush buttons and bumper stickers - and he said, 'And you think I was going to say no? People are people'."

Outside Boston city hall the mood was upbeat, if not euphoric, with supporters wearing badges showing Sesame Street's Ernie and Bert, and the slogan "Let them marry".

But many have pointed out that there is still a long way to go. Gay marriage has become the touchstone social issue in the forthcoming elections, with both presidential candidates opposed and President George Bush saying he will support an amendment to change the constitution to define marriage as a heterosexual institution.

It is still not clear whether same-sex marriages in Massachusetts will be recognised elsewhere in the country, particularly in states which have constitutionally excluded them. The governor of Massachusetts, who is also opposed, has invoked an old law to stop same-sex couples from outside the state coming in to get married, although many city clerks have said they will ignore it.

Across the US public opinion is shifting. A Gallup poll released yesterday showed that since December support for gay marriage has grown from 31% to 42%, while the number of those against it has fallen from 65% to 55%.

"Today is a significant victory for us," said Marianne Duddy-Burke, 43, as she waited with her partner of 10 years, Becky. "But fundamental change in society takes so much more than a court case."

"The floodgates have been opened here and I think it will be the law all over the country," said Rob Villegas, who said he was concerned that his marriage would not be recognised if he moved back to his home state of Texas. He and his partner of six years, Mike Normandin, planned to wait three days before they got married.

"We've been together six and a half years and I never had cold feet before now, because I never had to think about it. I never thought it would happen."

The fact that it did was largely down to Hillary and Julie Goodridge, who emerged from Boston city hall with their daughter Annie and their licence to the loudest cheer.

Three years ago they applied for a licence and were turned away. "I'll need two grooms first," said the woman behind the counter.

When they asked to speak to the department's director they were told: "No, you can't get married, and there's nothing you can do about it."

Their decision to challenge the law led to November's ruling from the Massachusetts supreme court that the ban on same-sex marriage was illegal, and it paved the winding path - through myriad legislative and legal challenges - to yesterday's milestone.

"Next to the birth of our daughter, this is the happiest day of our lives," Julie Goodridge said yesterday.

As the Goodridges headed towards the courthouse where they had once been turned down, a female police officer offered to hold Hillary's hand to protect her from the media scrum.

"Excuse me," chided Hillary mockingly. "That's my wife."