Europe’s vernaculars became codified written languages beginning with Castilian in 1492

Evidence

In 1492, a year well known also for some other events, a Spanish humanist called Antonio de Nebrija published a grammar of the Castilian language. This, as far as I am aware, is the first time that anyone had treated a colloquial language seriously. He tried to establish rules, and launched the process by which the Castilian dialect became the Spanish language. — Bernard Lewis, From Babel to Dragomans, 151

Categorization

• SEED: Nebrija timing his grammar with Granada’s fall and the expulsion of Jews is a rich angle on language-codification as imperial consolidation.