The bill passed the Senate, was rushed over to the House, which voted overwhelmingly to concur, and it's headed for the governor.
At a jubilant press conference, Gov. Christine Gregoire said she intends to sign the bill into law on Tuesday morning.
Bill sponsor Ed Murray said he expects a ballot measure challenge to the bill. He and Gregoire both vowed to fight any such challenge.
"We're ready," Murray said in an interview, predicting that voters will turn down such a measure.
"The state's changed," he said. "They know more gay and lesbian people."