Ben Garvin / The St. Paul Pioneer Press via AP Sen. Scott Dibble, DFL-Minneapolis, left, sponsor of the gay marriage bill in the Minnesota Senate, and his partner Richard Leyva greet a large, joyous crowd as they arrive at the Minnesota State Capitol in St. Paul, Minn. on May 13, before a Minnesota Senate debate on a bill that would make Minnesota the 12th state to legalize gay marriage and the first to pass such a measure out of its Legislature.

The Minnesota Senate gave final approval on Monday to a bill that will make the state the 12th in the United States to allow same-sex couples to marry and only the second in the Midwest.

The majority Democrat state Senate voted 37-30 to approve the bill legalizing gay marriage, putting Minnesota on the verge of becoming the third state in the nation to approve same-sex nuptials in May after Rhode Island and Delaware.

The state House approved the measure last week.

Democratic Governor Mark Dayton has said he will sign the bill on Tuesday. The law would take effect August 1.

Minnesota will join Iowa as the only other Midwestern state to permit gay marriage and the first to do so through legislation. Iowa has permitted same-sex marriage since 2009 under a state Supreme Court order.

The Minnesota House had been expected to be the bigger hurdle, but representatives voted 75-59 on Thursday to approve a bill with some Republican support.

The measure has at least one Republican sponsor in the Senate.

Senator Scott Dibble, the bill's architect, has said the stronger-than-expected vote from representatives was very encouraging and urged same-sex marriage supporters to continue active lobbying for the bill right up to Monday's vote.

Hundreds of supporters and opponents of the proposal to legalize same-sex marriage demonstrated at the Capitol on Thursday. Monday's atmosphere was very similar.

The vote on Thursday was a sharp reversal for Minnesota's legislature. Two years ago, Republicans controlled both chambers and bypassed the governor to put forward a ballot measure that would have made the state's current ban on gay marriage part of the state constitution.

Minnesota voters in November rejected that measure and also voted in Democratic majorities in both the state House and Senate, setting the legislature on the path toward Monday's vote.

Republican Senator Warren Limmer, a sponsor of the proposed amendment two years ago, has said the legislation will change how businesses work, clergy speak from the pulpit and school curriculums are shaped.

"Prior to the marriage amendment (vote) in November, many people were warning that this day would come," Limmer said in an interview last week.

Opponents of the bill have questioned whether the rights of religious groups and individuals who believe marriage should be only between one man and one woman would be protected. They also questioned the speed with which the measure was being approved.

Over several years, voters in more than two dozen states approved state constitutional provisions that define marriage as a union between a man and a woman. But in the past year, gay rights advocates won a series of victories.

In November, Maine, Maryland and Washington state became the first states to approve same-sex marriage at the ballot box.

Same-sex marriage is also legal in Massachusetts, Connecticut, New York, Vermont and New Hampshire. The District of Columbia also has legalized same-sex marriage.

Illinois state senators approved a bill in February, but the measure has not been voted on in the full House.

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