The Pennsylvania county which was last month ordered to stop issuing marriage licences to same-sex couples, is appealing against the decision.
Democrats in Montgomery county on Tuesday announced the appeal against the decision from 12 September.
County clerk D Bruce Hanes had issued over 170 marriage licences to same-sex couples, and had said he wanted to come down on the “right side of history”, deeming the state’s ban on equal marriage as unconstitutional.
Mr Hanes, who worked as Montgomery County’s Register of Wills, had said he wanted to come down “on the right side of history and the law” when he began issuing the licenses in late July.
He added: “Some people have said I’ve broken the law, which I may have done but I’ve broken an unconstitutional law.”
It was not immediately clear what the decision will mean for those same-sex couples who have already been issued with marriage.
Meanwhile in New Jersey, Governor Chris Christie is appealing the opposite. Last week Judge Mary Jacobson ordered that the state should being issuing marriage licences to same-sex couples as of 21 October. The Governor’s administration has gone to the Supreme Court for a decision.