A Missouri state judge overturned the ban on same-sex marriage on Wednesday, declaring the prohibition unconstitutional.

St Louis Circuit Judge Rex Burlison said that the state's ban against gay marriages denied individuals their due process and equal protection rights. Missouri Attorney General Chris Koster filed an appeal with the state Supreme Court the same day.

While the state is contesting the ruling, the attorney general's office chose not to file a stay on the decision, citing the US Supreme Court's refusal to grant stays in similar cases in Idaho and Alaska.

Following Judge Burlison's ruling, many same-sex couples applied for marriage licenses in Missouri. One of those couples was Kelley Harris, 35, and Kelly Barnard, 36, who travelled to St Louis with a photographer in tow. They had a wedding ceremony in 2003, and have two children, but were eager to make their union legal.

"We've already been living as a married couple — we have children, we have family — so it would be nice to have the legal backing," Harris told the Associated Press.

After being granted a marriage license, April Breeden, 38, and Crystal Peairs, 38, held an informal ceremony on steps of City Hall. "Time is of the essence," Peairs explained. "We wanted to make sure we got it taken care of today."

Gay marriage has been a contentious issue over the past two years, and bans against gay marriage have been reversed or are currently in litigation in all 50 states. St Louis City counsellor Winston Calvert said the existing law treated same-sex couples "second-class citizens", and applauded Judge Burlison's decision.

"Obviously this is a long time coming for so many gay and lesbian couples in the state of Missouri and the city of St Louis in particular," Calvert said. He was joined by St Louis Mayor Francis Slay.