At the Thurston County Courthouse five couples were married, including Jonathon Bashford, 31, and Matthew Wiltse, 29, both of Olympia.
The couple, together for 10 years, just had a large commitment ceremony in September when they registered as domestic partners, but said they wanted to be among the first to legally marry.
"We weren't going to wait one second longer," Wiltse said.
Last month, Washington, Maine and Maryland became the first states to pass same-sex marriage by popular vote. They joined six other states New York, Connecticut, Iowa, Massachusetts, New Hampshire, Vermont and the District of Columbia that had already enacted laws or issued court rulings permitting same-sex marriage.
Couples in Maryland also started picking up marriage licenses Thursday, though their licenses won't take effect until Jan. 1. Maine's law takes effect on Dec. 29. There's no waiting period in Maine, and people can start marrying just after midnight.
Washington Gov. Chris Gregoire and Secretary of State Sam Reed certified the election results of Referendum 74 on Wednesday afternoon, and the law took effect at 12:01 a.m. Thursday. Same-sex couples who previously were married in another state that allows gay marriage, like Massachusetts, will not have to get remarried in Washington state. Their marriages became valid here as soon as the law took effect.
The referendum had asked voters to either approve or reject the state law legalizing same-sex marriage that legislators passed earlier this year. That law was signed by Gregoire in February but was put on hold pending the outcome of the election. Nearly 54 percent of voters approved the measure.
The law doesn't require religious organizations or churches to perform marriages, and it doesn't subject churches to penalties if they don't marry gay or lesbian couples.
Married same-sex couples will still be denied access to federal pensions, health insurance and other government benefits available to heterosexual couples because the 1996 federal Defense of Marriage Act, known as DOMA, bars federal recognition of gay unions.
The U.S. Supreme Court on Friday said it will take up gay marriage sometime during the current term. Several pending cases challenge the federal benefit provision of DOMA, and a separate appeal asks the justices to decide whether federal courts were correct in striking down California's Proposition 8, the amendment that outlawed gay marriage after it had been approved by courts in the nation's largest state.