As the final vote count of the city assembly was announced — 39 in favor to 20 against — the crowd of gay and lesbian activists in Mexico City exploded into cheers, hugs and kisses. With a resounding majority, the Mexican capital had become the first city in Latin America to allow same-sex couples to marry and to have the same rights as heterosexual unions. A separate motion confirmed that the couples would be able to adopt children. "This is a huge triumph that has followed so many years of struggle," said campaigner Kin Castañeda, who stood next to her partner in the assembly gallery, the two women wearing identical white Mexican folk dresses. "It is a recognition of our basic rights. And that is a cause for celebration today."

The effect of the landmark vote on Monday was rapidly felt across the continent, from Patagonia to the Rio Grande, where other groups have been campaigning for gay marriage rights. On Wednesday, 10 same-sex couples filed legal motions in a court in Rosario, Argentina, demanding their right to marry. In neighboring Chile, a column in the newspaper Paradiario was headlined, "Gay Marriage Approved in Mexico. In Chile When?" In the swampy Mexican state of Tabasco, 20 gay couples sent a motion to the state legislature asking to allow them to tie the knot. Mexico City's precedent, the activists hope, will have a domino effect across the hemisphere.