(CNN) -- Washington is joining two other states that have passed ballot measures making same-sex marriage legal, CNN is projecting.
After nearly two days of counting, the voting broke down this way: 1,269,917 residents are in favor of it while 1,146,439 are not. By Friday, 75% of precincts were reporting results.
Voters in Maine and Maryland also approved similar measures on Tuesday.
In Maryland, 51.9% of voters passed same-sex marriage.
Maine could begin granting marriage licenses to couples as early as mid-December.
Recent national surveys have shown shifting attitudes toward same-sex marriage, with a majority of Americans now approving of marriages between two men or two women. A June CNN/ORC poll, for example, reflected such a shift in opinion in the U.S.
Election Day brought two additional gains for proponents of same-sex marriage: Wisconsin elected America's first openly lesbian senator, Democrat Tammy Baldwin, and President Obama became the first president to openly support same-sex marriage and get re-elected.