Civil unions have technically been in existence in various forms for around six centuries. Historians point to medieval France’s use of the affrèrement — betrothment — contractual relationship, where the couple would share un pain, un vin, et une bourse — one bread, one wine, and one purse. More recently gay and lesbian activists around the world have been campaigning for several decades for more rights — and they’ve found a good deal of success.

On this day, October 1, in 1989, the first same-sex union law in the world took effect in Denmark, extending to same-sex couples all the legal rights and privileges of opposite-sex couple, except where the law refers specifically to males or females.

Invoking the language of the Civil Rights era, the law points to their groups as “separate but equal,” which the U.S. Supreme Court struck down in a landmark case. As Evan Wolfson, the founder and executive director of Freedom to Marry, a gay-marriage advocacy group, put it, “Marriage in the United States is a civil union; but a civil union, as it has come to be called, is not marriage.”