Geiger and Nelson, who were among the plaintiffs in the court case, were the first same-sex couple to marry legally in Portland. The ceremony was held in the Multnomah County Building's lobby less than an hour after U.S. District Judge Michael McShane issued his ruling.
The two women married in 2004, when Multnomah County decided to give licenses to same-sex couples. But the marriage became invalid when Oregon voters approved a referendum limiting marriage to heterosexual couples.
McShane's decision came just over 10 years after gay marriage became legal in Massachusetts by a decision of the state Supreme Court. In Oregon, state officials have declined to appeal the ruling.
The judge, who is openly gay, wrote an unusually personal opinion, saying homosexuals have been subjected to "cruelty, violence, and self-loathing." He said opponents fear "a slippery slope that will have no moral boundaries."
"To those who truly harbor such fears, I can only say this: Let us look less to the sky to see what might fall; rather, let us look to each other ... and rise," he said.
The U.S. Supreme Court decision last year overturning the Defense of Marriage Act has changed the legal landscape. Federal judges in several states and a state judge in Arkansas have ruled that laws or constitutional amendments banning gay marriage violate the Equal Protection Clause of the U.S. Constitution, although most of those decisions have been stayed pending appeal.
In Oregon, McShane refused to allow the National Organization for Marriage to intervene in the case and a federal appeals court refused to grant a stay to give the group time to make its case to become a party.
Tina Kotek, speaker of the Oregon House, said after the ruling that she and her partner, Aimee Wilson, will marry this year after "a 10-year engagement."
"Today's historic ruling means that all Oregonians will have the legal right to marry the person they love," she said in a statement.