Whitinsville, Mass. ? Twenty years after he met the love of his life, nearly five years after their wedding helped make history, it took a nasty bout of pneumonia for Gary Chalmers to fully appreciate the blessings of marriage.

“I was out of work for eight weeks, spent a week in the hospital,” Chalmers said. “That was the first time I really felt thankful for the sense of the security we had, with Rich there, talking with the physicians, helping make decisions. … It really made a difference.”

At stake was the most basic recognition of marital bonds — something most spouses take for granted. But until May 17, 2004, when Chalmers and Richard Linnell were among a surge of same-sex couples marrying in Massachusetts, it was legally unavailable to American gays and lesbians.

Since that day, four other states — Connecticut in 2008, and Iowa, Vermont and Maine this year — have legalized same-sex marriage, and more may follow soon. A measure just approved by New Hampshire’s legislature awaits the governor’s decision on whether to sign. But Massachusetts was the first, providing a five-year record with which to gauge the consequences.

At the time of those first weddings, the debate was red-hot — protests were frequent, expectations ran high that legislators would allow a referendum on whether to overturn the court ruling ordering same-sex marriage. Now, although Roman Catholic leaders and some conservative activists remain vocally opposed, there is overwhelming political support for same-sex marriage and no prospect for a referendum.

According to the latest state figures, through September 2008, there had been 12,167 same-sex marriages in Massachusetts — 64 percent of them between women — out of 170,209 marriages in all. Some consequences have been tangible — a boom for gay-friendly wedding businesses, the exit of a Roman Catholic charity from the adoption business — and some almost defy description.

Mary Bonauto, lead lawyer in the landmark lawsuit, said, “I know people who’d been together 20 years who say, ‘Getting married — it knocked my socks off.”‘

Fading opposition

One of the striking developments, since 2004, is the fading of opposition to gay marriage among elected officials in Massachusetts.

When the state’s Supreme Judicial Court ruled in 2003 that banning same-sex marriage was unconstitutional, there seemed to be sufficient support in the Legislature for a ballot measure that would overturn the decision. But a gay-marriage supporter, Deval Patrick, was elected governor; and in 2007 lawmakers rejected, 151-45, a push for a referendum.

The view now contrasts with 2003-04, when the debate was wrenching for legislators such as Sen. Marian Walsh. Her district, including parts of Boston and some close-in suburbs, is heavily Catholic and socially conservative. Many supported overturning the high court’s ruling.

“I had hundreds of requests to meet with people on both sides,” Walsh said. “Everyone wanted to know how was I going to vote.”

She read up on the law, wrestled with her conscience, and finally decided the court was correct — and there should be no referendum.

“I came to the decision that it really is a civil right — that the constitution was there to protect rights, not to diminish rights,” she said.

The reaction? Embittered constituents, hate mail and death threats, rebukes from Catholic clergy, she said, but she won re-election in 2004 and again in 2006.

‘A different world’

Neither the federal government nor the vast majority of other states recognize Massachusetts’ same-sex unions. Partly as a backlash to Massachusetts, 26 states have passed constitutional amendments since May 2004 explicitly limiting marriage to male/female unions.

Even the 2010 census, under the Defense of Marriage Act, likely won’t record legally wed couples in Massachusetts and elsewhere as married.

Gay & Lesbian Advocates & Defenders, the Boston legal firm which won the same-sex marriage case, filed a new lawsuit in March challenging the portion of the act that bars the federal government from recognizing same-sex marriages. But for now, non-recognition can be stinging.

After Michael and Rick McManus of Charlton married in 2006, they honeymooned in Panama, and on return to the United States were told at the immigration booth that they had to go through separately because U.S. law didn’t consider them married.

Michael and Rick have subsequently adopted a son, turning 2 on May 7, and a daughter, almost 1. They plan to limit international travel until the federal policy changes.

“There’s a sense of security for our family here,” Michael said. “But when we leave this state, it’s a very different world.”