Susan Shepherd, right, and Marcia Lynn Hams, center, are accompanied by their son Peter Hams as they cut the cake on the first anniversary of the legalization of same-sex marriage in Cambridge.

One year and 638 licenses later, Cambridge politicians, families, and supporters gathered yesterday at City Hall to celebrate the anniversary of legal same-sex marriage while also reflecting on the uncertain future of those rights in Massachusetts.

“Last year was a time for celebration...but now is a time to recognize that the rights and privileges we have, others are trying to take them away,” said Mayor Michael A. Sullivan, speaking before the crowded chamber.

Yesterday afternoon’s celebration came one year after the city allowed same-sex couples to file for marriage licenses at midnight on May 17, 2004—the first moment when a landmark state court ruling legalizing same-sex marriage went into effect.

Granting marriage licenses to same-sex couples “fulfilled our mission to fight for freedom for all,” said Councillor Kenneth E. Reeves ’72 before the ceremony. Reeves said the fact that Cambridge was the first city in the nation to offer those licenses was ”perfectly apropos” for Cambridge’s liberal reputation.

A proposed state constitutional amendment banning same-sex marriage but allowing civil unions passed a vote of the legislature last year. The proposal needs the vote of a newly-elected legislature in 2005-06 before it could be put to voters in a referendum.

Ryan R. Thoreson ’07, a co-chair of Harvard’s Bisexual, Gay, Lesbian, Transgender, and Supporters Alliance who attended yesterday’s celebration, called a ban in Massachusetts “a very real chance.” But “the threat has lessened since last year,” Thoreson added, referring to the shift in legislative leadership toward same-sex marriage supporters.

Thoreson and three other Harvard students traveled together to yesterday’s ceremony, which included photo and video retrospectives of last year’s celebration.

The event also featured the cutting of an anniversary cake by Marcia Hams and Susan Shepherd of Cambridge, who became the first same-sex couple to file for a marriage license last year after waiting in line for 24 hours.

Hams’ and Shepherd’s son Peter Hams, a senior at the College of William and Mary, spoke during the ceremony.

“A lot of people ask me, what’s the difference? Why does it matter?” Peter Hams said, referring to his parents’ marriage.

“It’s the first time I can speak openly about my family with pride.”

Another child of same-sex spouses present at the celebration was Jesse McGleughlin, a seventh-grader at the Graham and Parks School in Cambridge.

“As young children, all of us were free-minded...[but] I hate myself for hiding my life as I grow up,” McGleughlin said.

“I’m not proud that I need a law to acknowledge my family,” she added.

Statistics released by the state indicate that same-sex couples who married over the last year were much older than their heterosexual counterparts, and many of the spouses who participated in the celebration last night, including Hams and Shepherd, have been together for decades.