Minnesota Gov. Mark Dayton is set to sign the Freedom to Marry Bill into law on the steps of the State Capitol today at 5 p.m. local time.

The bill passed by a vote of 37 to 30 in the state Senate Monday, after more than four hours of passionate yet respectful speeches on both sides. Dayton had expressed support for same-sex marriage before the bill passed and was expected to sign it.

Minnesota joins 11 other states and the District of Columbia in legalizing gay marriage, meaning that about 18 percent of the country's population has the option to marry regardless of gender. Half of those states approved gay marriage after President Obama expressed support for it in May 2012.

Just two years ago, the Minnesota Senate and House passed a very different bill: a constitutional amendment that would have banned gay marriage in the state. In less than a month it passed through both chambers, landing a spot on the 2012 ballot. But voters rejected the amendment in November.

The 16-month battle leading up to its ultimate failure among Minnesotans was one of the most expensive in the state, according to Minnesota Public Radio.

"The main group opposing the amendment, Minnesotans United for All Families, brought in nearly $10 million in cash donations. Minnesota for Marriage, the group leading the fight to pass the amendment, raised more than $5 million," MPR reported the day after the election.

The bill Dayton signs today is slightly different from those in other states, because it specified that it pertains to "civil marriage," whether in same-sex or opposite-sex marriages.

"This is done to emphasize that our laws and our statutes only pertain to the legal aspects of marriage, maintain that distinction so we can look to the law and know that it does not intrude on religious beliefs and practice," Minnesota State Sen. Scott Dibble said on the Senate floor Monday. "It simply affirms what was already true and has always been true…that the laws that pertain to marriage are laws that only deal with civil matters and don't reach into private firmly held religious beliefs or practice."