The United States, Donald Trump says, “is the only country in the world” that grants citizenship to babies born within its borders. He’s wrong, of course. Tanzania, Pakistan, and France all grant some form of birthright citizenship.
But birthright citizenship is ultimately an American ideal. That is, all of the Americas. Nearly every country in the Western Hemisphere grants citizenship to children born in its territory irrespective of the nationality of their parents. It’s part of the promise of the New World, that the Western Hemisphere would be, as the American revolutionary Thomas Paine said of the United States, an “asylum” for humanity. “Open,” echoed George Washington, “to receive not only the opulent & respectable” but the “oppressed & Persecuted of all nations.” The children of those oppressed and persecuted would be citizens by right.
The legal term for birthright citizenship is jus soli, or “by right of soil”—in contrast to jus sanguinis, which assigns citizenship to children based on the national identity of one or both of their parents, an identity that could be defined by bloodline, race, or religion. Mexicans were the first to write jus soli into a constitution, in 1814, during their war of independence against Spain. In bright, unambiguous language, the rebels stated that “all those born in La Mexica América are considered citizens.” By “all,” they meant all. Having declared the abolition of both chattel slavery and Indigenous tribute and servitude, Mexican revolutionaries intended to make everyone, regardless of skin color, a member of the nation, but Spanish troops retook Mexico before this constitution could go fully into effect.
The three-century-old Spanish empire was obsessed with blood—how it conveyed lineage and, in the Spanish view, confirmed virtue. Jus sanguinis had been the law of the land, and a good part of the empire’s massive bureaucracy worked to keep track of ancestry, issuing certificates of purity certifying that no taint of Jewish, Muslim, Native American, or African blood flowed in the bearer’s veins.
Mexico was just one front in a hemisphere-wide war against Spanish rule, which began in 1810 and didn’t end until 1826, when revolutionaries overran royalism’s last bastion, the Pacific port city of Callao, Peru. With all of Spanish America (save Cuba and Puerto Rico) now free, the region’s republican leaders were eager to leave Spain’s blood medievalism behind, to create a modern legal system for the Americas.