The American Civil Liberties Union on Tuesday launched a legal challenge to Pennsylvania’s ban on gay marriage, part of a flurry of lawsuits filed since last month’s Supreme Court ruling on federal benefits for same-sex couples.

In the lawsuit filed Tuesday in Harrisburg, Pa., the ACLU is representing 23 plaintiffs: 10 gay couples, two children of one of the couples, and the surviving partner in a same-sex couple that was together for 29 years.

James Esseks, who directs the ACLU’s Lesbian Gay Bisexual Transgender & AIDS Project, said the group hopes to secure the right for gay couples to marry in Pennsylvania, force the state to recognize same-sex marriages performed elsewhere and increase pressure on the Supreme Court to ultimately rule on whether same-sex marriage should be legal across the nation.

“Pennsylvania recognizes straight people’s marriages from Maine and New York, but it doesn’t recognize gay people’s marriages from Maine and New York,” Esseks said. “The question is, why?”

Opponents of same-sex marriage questioned why activists were seeking redress in court rather than through a ballot initiative in Pennsylvania. Under Pennsylvania law, the state legislature has to approve resolutions before they can be put on the ballot for a direct vote, and no resolution endorsing gay marriage has passed at this point.

“We think it’s very telling gay marriage advocates are using the courts so heavily,” said Thomas Peters, communications director for the National Organization for Marriage. “They only support the voice of the people when they think it will go their way.”

Peters said his group is focused on Indiana, where Gov. Mike Pence (R) has urged the legislature to pass a constitutional amendment banning same-sex marriage so it can be put before the voters as a ballot initiative in 2014. The organization is also involved in an ongoing legislative fight in Illinois over whether to legalize gay marriage there.

On the other side, the ACLU said it would also amend a North Carolina lawsuit to include a demand that the six gay couples who filed the case should be allowed to marry. The lawsuit is focused on challenging the state’s ban on second-parent adoption, where one partner adopts the other partner’s child.

Esseks also said the ACLU plans to file a lawsuit challenging Virginia’s same-sex marriage ban “quite soon.”

A pro-gay-marriage group called Freedom to Marry also announced Tuesday that it would spend $500,000 on state initiatives to legalize gay marriage, including $250,000 on an effort to reverse Oregon’s ban through a ballot initiative next year. The group said it had hired Richard Carlbom, who spearheaded the successful effort to legalize gay marriage in Minnesota, as its director of state campaigns.

Helena Miller and Dara Raspberry, who are plaintiffs in the Pennsylvania lawsuit, met in Brooklyn in 2006 and were married in Connecticut in 2010. They moved to Philadelphia later that year in part to be closer to Miller’s family as they prepared to have children.

Miller gave birth to the couple’s daughter, Zivah, on May 28. While Raspberry would have automatically been named on the birth certificate as the other parent in a state where gay marriage is legal, the couple has had to hire a lawyer and go through the process of second-parent adoption in Pennsylvania.

“We have a wonderful family and we get wonderful support from our family and friends,” Miller said in an interview. “Unfortunately by moving to Pennsylvania, we effectively became unmarried.”