Marriage licenses were available on Thursday at 12:01 a.m., and courthouses around the state opened as early as midnight to start weddings, the Associated Press reported.
"We're so proud to live in this state that recognizes love and commitment," said Sarah Cofer, who wed her fiancee Emily at Seattle's King County Courthouse as their nine-month-old daughter Carter looked on, the AP reported.
They were followed by 11 other couples, who took their vows in front of judge Mary Yu in 30-minute intervals.
Other courthouses, including Seattle City Hall, announced that they would be open for several hours Sunday, and local judges have volunteered their time to marry couples there, according to Reuters.
"I'm proud to be a witness to an extraordinary event in our history," Judge Yu told the AP, adding that the marathon nuptials were "an opportunity to recognize that marriage and love and family are good."
Washington, along with Maine and Maryland, became the first states to pass same-sex marriage by popular vote in elections last month. The states joined New York, Connecticut, Iowa, Massachusetts, New Hampshire, Vermont, as well as the District of Columbia.
Maryland's same-sex couples also were able to pick up their marriage licenses on Thursday, though those won't take effect until January 1, the AP reported.
However, the states' married gay couples still won't have access to federal pensions, health insurance, and other government benefits because of the Defense of Marriage Act, known as DOMA, which does not recognize same-sex marriages at the federal level.
On Friday, the US Supreme Court said it would take up gay marriage cases during their current term, according to the AP.