Guests celebrate the unveiling of a plaque by Amsterdam Mayor Job Cohen on Feb. 14, 2007, commemorating the first same-sex marriage in Amsterdam. (Robin Utrecht/AFP/Getty Images)

With a landmark Supreme Court decision Friday, the United States became the 17th country to legalize same-sex marriage. But what was the first?

The Danish were the first to grant same-sex unions almost the exact same rights as marriages, with its Registered Partnerships Act of 1989. However, the law stopped short of calling same-sex unions "marriages," and couples could not be married in the Danish state church or adopt a child.  Even so, the law was viewed as an important stepping stone at the time.

''The only way to be able to move anything is to be open about it," Eigil Axgil, 67, who entered a union with his partner on the day the law passed, told the New York Times in 1989. ''You have to say that this is the way I am so society can be open to you. If everyone follows this lead in Denmark, if everyone goes out and says this is the way they are and go out of the closet, this event will also happen in the rest of the world.''

And people did follow Denmark's lead: During the 1990s, a number of other countries and regions introduced laws that granted same-sex unions similar rights to marriages. It wasn't until 2001, however, that a country fully legalized same-sex marriage. That country was the Netherlands.

The Dutch law went further than Denmark's, effectively eliminating any distinction at all between heterosexual and homosexual marriage. When it passed parliament in 2000 (it would not become law until a few months later), The Washington Post's Keith Richburg noted that it seemed to "add to the Netherlands' reputation in Europe and beyond for enacting laws that many hail as signs of tolerance and others decry as laxity."

The vote had been a foregone conclusion, and government officials seemed bemused by the global attention. "The discussion was years ago," a spokeswoman for the Dutch Embassy told The Post. "We are always a bit ahead of other countries. We had those discussions years before other countries even started."

Again, other countries followed the Dutch lead. Belgium legalized same-sex marriage in 2003, and many others have since then (the Danish fully legalized it in 2012). So far in 2015, four countries have legalized same-sex marriage, including the United States.

So how has the Netherlands coped since legalizing gay marriage? Even some of its fiercest Dutch critics now say it was a good move.

"At the time I opposed same-sex marriage, I was led by fear," Hannie van Leeuwen, leader of the Christian Democrat party and opponent to the gay marriage law, was reported to have said just a few years later. "Having seen so many happy gay and lesbian couples getting married, I realize I was wrong. I don't understand anymore what made me treat gays and lesbians differently from other citizens."

And evidence suggests that while discrimination was far from totally eradicated by the Netherland's gay marriage law, the institution of marriage has suffered no ill effects at all.

"Heterosexual couples did not turn away from the institution of marriage, nor did the world isolate my country," Boris Dittrich, a former member of Netherland's parliament, wrote in 2011. "Civilization as we know it did not end. And, as far as I can tell, God did not punish the Netherlands."

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