Maryland Gov. Martin O'Malley speaks in support of a same-sex marriage bill during a news conference at the governor’s mansion in January 2012. (AP Photo/Patrick Semansky)

Maryland Gov. Martin O’Malley (D) and his wife are planning to welcome close to 200 supporters of same-sex marriage to the governor’s mansion Friday night to celebrate the arrival of gay nuptials in the Free State.

Invitations to the event bill it as a “holiday celebration.” But the cover features a photo of the black-and-white “Dignity” button that O’Malley wore as he championed the legislation this year, and aides confirmed the purpose is to thank supporters. That includes a few celebrities, such as Baltimore Ravens linebacker Brendon Ayanbadejo.

O’Malley signed a same-sex marriage bill into law in March, but it was petitioned to referendum by opponents. Last month, Maryland voters supported a ballot measure upholding the new law, 52 percent to 48 percent. Prior to Election Day, no other state had authorized gay marriage by a popular vote.

“This is an opportunity to celebrate its passage and thank the many, many people and organizations who helped ensure the passage of the bill and the referendum,” said O’Malley spokeswoman Raquel Guillory. She said the state will cover the cost of the event.

On Thursday morning, O’Malley signed a proclamation making the election results official. That move allows clerks and circuit courts to immediately start issuing marriage licenses to gay couples that will take effect on Jan. 1, when the new law takes effect.

Friday night’s event in Annapolis is expected to draw a mix of legislators, clergy, union members and others active in the fight.

According to O’Malley aides, those invited who have yet to RSVP include Josh Charles, an actor and Baltimore native; and the Rev. Al Sharpton, the civil rights leader, former presidential candidate and cable-television personality.

Ayanbadejo, the Ravens player, became one of the most visible champions of the new law this year, appearing with O’Malley at a fundraiser that drew widespread media attention.

An unofficial afterparty is planned at a local wine bar in Annapolis following O’Malley’s gathering, aides said.