(CNN) -- Breaking ground is nothing new in the nearly six-decade relationship of Del Martin and Phyllis Lyon.

The lesbian couple were the first to participate in a 2004 challenge of California laws against same-sex marriage, exchanging wedding vows only to see the ceremony voided later.

But on Monday, Martin, 87, and Lyon, 84, exchanged vows again. This time, California law -- at least for now -- was on their side.

"I think it's a wonderful day and I have to thank our mayor for most of it," Lyon said. "I'm very happy and very grateful for all of you."

San Francisco Mayor Gavin Newsom, who helped launch the series of lawsuits that led the court to strike down California's one-man-one-woman marriage laws, presided at their wedding at City Hall.

Well-wishers cheered when the couple emerged from Newsom's office after the ceremony.

"When you consider these two women, who have been denied their rights for 55 years -- put yourself in their shoes and you start to feel a little bit differently," said Newsom, adding that allowing gay and lesbians to marry is about giving them the respect and dignity they deserve.

The wedding took place at the same time a California Supreme Court ruling allowing same-sex marriages takes effect.

"It's really just amazing the progress we've made," Lyon told the San Francisco Chronicle.

The march to matrimony has taken a long time for Lyon and Martin, but marriage wasn't always the goal.

They met in the early 1950s in Seattle, Washington, where they worked as editors of construction trade publications, before falling in love and buying a house together in San Francisco later that decade.

In 1955, they founded the nation's first lesbian organization, the Daughters of Bilitis. In the 1960s, they tried to get California lawmakers to introduce anti-discrimination bills and successfully persuaded some police officers to stop harassing gays and lesbians at bars, according to The Associated Press.

"We didn't give a damn about getting married. We just wanted to get a law that said you can't fire us because we are gay," Lyon told the AP.

In 2003, filmmaker Joan E. Biren released "No Secret Anymore: The Times of Del Martin and Phyllis Lyon," a 57-minute documentary focusing on the couple's activism and relationship.

That year, the couple spoke to The Noe Valley Voice, a newspaper covering their San Francisco neighborhood, about the film and their drive to advance the rights of lesbians.

"We wanted our full rights and responsibilities," Martin told the Voice in 2003.

Lyon said during the interview she and Martin had no particular secret on how to keep a relationship going for decades.

"If we had a secret, we would have written a book and made a million dollars," Lyon told the Voice. "We love each other, we have similar interests. Our lives were very similar even before we met."

In 2004, San Francisco officials allowed gay couples in the city to wed, prompting a flood of applicants to the City Hall clerk's office. The officials chose Lyon, then 80, and Martin, then 83, to take the first vows.

The state Supreme Court voided those unions. Lyon and Martin, however, joined more than 20 other couples as plaintiffs in a lawsuit challenging the state's marriage laws.

The California Supreme Court on May 15 struck down the state's ban on same-sex marriage, paving the way for Lyon and Martin and other same-sex couples to marry in the state as soon as the ruling takes effect Monday evening.

"We're not getting younger," Martin told the Chronicle last week.

Though some other county offices will stay open late Monday to accommodate same-sex couples, clerks throughout the state expect a larger number of couples Tuesday morning. Video Gay court clerk plans to be among first to marry ?

Robin Tyler and Diane Olson, one of the first couples to obtain a marriage license Monday evening, rushed outside the courthouse in Beverly Hills for their Jewish wedding ceremony.

There, they were greeted by a crowd of family, friends, supporters -- and a few opponents protesting the same-sex marriages with signs reading "repent."

"It's not about us," Tyler said. "It's about the entire movement that helped make this day possible."

Opponents have said they've collected enough signatures to call for a statewide vote on a constitutional amendment that would define marriage as between a man and a woman. The California secretary of state must verify the signatures to clear the way for a November vote on the proposed amendment.

Until then, same-sex marriages are expected to go ahead. San Francisco Mayor Gavin Newsom, one of the officials who spearheaded the 2004 same-sex marriages, will officiate Lyon and Martin's ceremony Monday.

Kate Kendall, executive director of the National Center for Lesbian Rights, told the Chronicle that Lyon and Martin are rightly in the spotlight more than 55 years after their relationship began.

"It would not be happening if it were not for Del and Phyllis," she told the Chronicle.

Martin's daughter, Kendra Mon, who was born 66 years ago as a result of Martin's brief marriage to a man, told the Chronicle she will be at Monday's ceremony.

"It's really a big deal for them and for me to have this happen at this point in their lives," Mon told the Chronicle. "It's like icing on the cake and a reminder of how far we've come."