Denmark was the first state to recognize a legal relationship for same-sex couples, establishing "registered partnerships" very much like marriage in 1989.
In 2001, the Netherlands became the first nation in the world to grant same-sex marriages.
Same-sex marriages are also granted and mutually recognized by:
Belgium (2003)
Spain (2005)
Canada (2005)
South Africa (2006)
Norway (2009)
Sweden (2009)
Portugal (2010)
Iceland (2010)
Argentina (2010)
Denmark (2012)
Brazil (2013)
France (2013)
Uruguay (2013)
New Zealand (2013)
In Mexico (2013), same-sex marriage is recognized in all 31 states but only performed in Mexico City and in Quintana Roo State.
In the United States (2013), thirteen states and the District of Columbia permit same sex marriage, beginning with Massachusetts in 2004 and Connecticut in 2008.
Same-sex marriage was legalized in the United States on June 26, 2015, when the Supreme Court ruled in the case Obergefell v. Hodges that same-sex couples have the fundamental right to marry under the Fourteenth Amendment to the United States Constitution.
The first country to legalize same-sex marriage was the Netherlands in 2001.
The legalization of same-sex marriage varies by country and region. It has been legalized in many countries around the world, with more countries continuing to recognize it. To know when same-sex marriage will be legalized in a specific location, it is best to refer to the latest legal developments and advocacy efforts in that particular area.
If by "illegal" you mean "against the law," then none. There is no state in the US where same-sex marriage is considered a crime. In fact, in most US states, same-sex marriage is legally recognized. (See related questions below: "What US states have legalized same-sex marriage" and "What US states have banned same-sex marriage.")
In some states in the United States, minors can get married without parental consent through a court order in cases of pregnancy or parental approval. As of 2021, there are no states that explicitly allow underage marriage for same-sex couples. Marriage laws vary by state and it is recommended to consult legal resources for up-to-date information on underage marriage laws.
Slavery was officially legalized in Georgia in 1750 by the Georgia Trustees.
Same-sex marriage has not been legalized in Laos.
No countries in the Balkans have legalized same-sex marriage.
No country in Central America has legalized same-sex marriage.
No former Soviet republics have legalized same-sex marriage.
No predominantly Muslim countries have legalized same-sex marriage.
Same-sex marriage was legalized in North Carolina on October 9, 2014.
Same-sex marriage was legalized in British Columbia on July 8, 2003.
Same-sex marriage was legalized in the Canadian province of Saskatchewan on November 5, 2004.
As of December 20, 2013, about 33% of US states have legalized same-sex marriage.
Same-sex marriage was legalized in the Canadian province of Nova Scotia on September 24, 2004.
Same-sex marriage was legalized in the Canadian province of Newfoundland and Labrador on December 21, 2004.
Same-sex marriage was legalized in the Canadian province of New Brunswick on June 23, 2005.