OLYMPIA, Wash. -

Voters in Washington state have approved gay marriage, joining Maine and Maryland as the first states to pass same-sex marriage by popular vote.

Referendum 74 asked people to approve or reject a law legalizing same-sex marriage that Washington legislators passed earlier this year. The law was signed by the governor but was on hold pending the election's outcome.

Washington is one of four states where voters were asked about the issue this election cycle. Maryland and Maine approved gay marriage Tuesday night, while Minnesota voters rejected a proposed constitutional amendment to ban it.

The District of Columbia and six states -- New York, Connecticut, Iowa, Massachusetts, New Hampshire and Vermont -- already allow gay marriage. But their laws were enacted either by lawmakers or court rulings.

“Washington has made history and I couldn’t be prouder. Voters stood up for what is right and what is just and said that all Washington families are equal under the law. I am proud that our LGBT families will no longer be treated as separate but equal, they will be equal," Governor Chris Gregoire said in a written statement Thursday afternoon. "This is a day that historians will look back on as a turning point for equality."