On a momentous night for LGBT equality, the US west coast state of Washington followed Maine and Maryland in passing a referendum in support of marriage rights for gay couples, and Minnesota voted against outlawing equal marriage.

Although Washington’s legislature initially legalised the measure in February of this year, opponents succeeded in gathering enough signatures to force a state ballot.

The full result of Wednesday morning’s victory won’t be known for a few days due to the state’s voting system.

However, the Seattle Times said those in favour of Washington’s Referendum 74 were ahead with 52% of the vote, by the early hours of this morning.

Gay couples could apply for marriage licenses as early as 6 December 2012.

Speaking to the crowd after returns were announced, an emotional Washington State Senator Ed Murray said: “We celebrate tonight not the victory of one set of Washingtonians over another; instead, we celebrate the belief that all families should be treated fairly.

“We celebrate those who over the decades, despite scorn and discrimination, built this movement and made this day possible.”

Last month, Washington-based Microsoft owner Bill Gates and his wife Melinda donated $500,000 (£313,000) towards efforts to legalise equal marriage in the state.

Meanwhile, Minnesota has voted down Amendment 1, a constitutional amendment that would have defined marriage as being a union solely between a man and a woman.

The state became the first in the country to vote against such an amendment on the ballot when results were announced early on Wednesday morning.