Same-sex couples began exchanging vows in Massachusetts Monday, marking the first time a state has granted gays and lesbians the right to marry and making the United States one of four countries where homosexuals can legally wed.

Tanya McCloskey, 52 and Marcia Kadish, 56, of Malden, went at a breakneck pace to fill out paperwork, get a waiver from the usual three-day waiting period, then return to city hall -- where they got their marriage license and exchanged vows.

At 9:15 a.m., Cambridge City Clerk Margaret Drury told the couple: "I now pronounce you married under the laws of the Commonwealth of Massachusetts."

It was among the first -- if not the first -- same-sex weddings anticipated to take place throughout the state on Monday, the day that under a court order same-sex couples could wed.

"It was really important to us to just be married. We want to be married as soon as we possibly can. Part of it is, we don't know what the Legislature is going to do," McCloskey said.

At the stroke of midnight, Cambridge officials threw open its doors to couples wishing to fill out marriage license applications. Within hours, judges began issuing waivers to the usual three-day waiting period.

Among those with wedding plans were the seven couples who brought the lawsuit that eventually led the state's highest court to declare gay marriage legal, breaking a barrier many never believed would fall and putting the United States among four countries where gays can marry.

The moves came against the backdrop of scattered protests but a largely festive party atmosphere.

"I'm proud of this state," said John Meuneir, 43, of Boston, who arrived at City Hall in Boston with his partner, Jim Flanagan, 42, more than two hours before the scheduled 8 a.m opening.

In Cambridge, more than 260 couples filled out application forms for marriage licenses in the wee hours. A throng that police estimated was more than 5,000 people converged on city hall, including some heterosexuals there to witness history in the making.

Massachusetts was thrust into the center of a nationwide debate on gay marriage when the state's Supreme Judicial Court issued its narrow 4-3 ruling in November that gays and lesbians had a right under the state constitution to wed.

In the days leading up to Monday's deadline for same-sex weddings to begin, opponents looked to the federal courts for help in overturning the Supreme Judicial Court's ruling. On Friday, the U.S. Supreme Court declined to intervene.

The SJC's ruling touched off a frenzy of gay-marriages across the country earlier this year, emboldening officials in San Francisco, upstate New York, and Portland, Ore., to issue marriage licenses as acts of civil disobedience. Even though courts ordered a halt to the wedding march, opponents pushed for a federal constitutional ban on gay marriage, which President Bush has endorsed.

The SJC's ruling also galvanized opponents of gay marriage in Massachusetts, prompting lawmakers in this heavily Democratic, Roman Catholic state to adopt a state constitutional amendment that would ban same-sex marriage but legalize Vermont-style civil unions. The earliest it could wind up on the ballot is 2006 -- possibly casting a shadow on the legality of perhaps thousands of gay marriages that take place in the intervening years.

Massachusetts joins the Netherlands, Belgium and Canada's three most populous provinces as the only places in the world where gays can marry. The rest of Canada is expected to follow soon.

The city of Cambridge, a liberal bastion that is home to Harvard University and the Massachusetts Institute of Technology, opened its doors to couples at midnight, and remained open until about 4:30 a.m. to accommodate the people who flocked there to make history.

The first couple to receive marriage paperwork was Marcia Hams, 56, and her partner, Susan Shepherd, 52, of Cambridge. After 27 years together, they sat at a table across from a city official shortly after midnight, filling out forms as their adult son looked on.

"I feel really overwhelmed," Hams said as they left the clerk's office and walked through a throng of reporters. "I could collapse at this point."

About 15 protesters, most from Topeka, Kansas,-based Westboro Baptist Church, stood near City Hall carrying signs. The group, led by the Rev. Fred Phelps Sr., travels around the country protesting homosexuality.

Out-of-state gay couples are likely to challenge Massachusetts' 1913 marriage statute, which bars out-of-state couples from marrying in Massachusetts if the union would be illegal in their home state. Gov. Mitt Romney, a gay-marriage opponent, has said the law will be enforced and clerks who give licenses to nonresidents may face legal implications.

Still, local officials in Provincetown, Worcester and Somerville, have said they will not enforce Romney's order and will give licenses to any couples who ask, as long as they sign the customary affidavit attesting that they know of no impediment to their marriage.

Sure enough, Chris McCary, 43, and his partner of six years, John Sullivan, 37, of Anniston, Ala., were first in line outside town hall in Provincetown on Monday morning.

"This is the most important day of my life," said McCary.

Both sides in the debate say the issue may figure prominently in the November elections across the country.

Candidates for Congress could face pressure to explain their position on a proposed federal constitutional amendment that would ban gay marriage, and voters in several states will consider similar amendments to their state constitutions.

Married couples are entitled to hundreds of right and protections under Massachusetts law, including the ability to file joint state tax returns, automatic preference for making medical decisions for a disabled spouse and workers' compensation benefits. But other rights, such as the ability to jointly file a federal tax return, are not available because federal law defines marriage as between a man and a woman.