I’d noticed that most of the countries of central and south America speak Spanish, except Brazil. I’d just assumed that the Portuguese only managed to grab Brazil while the Spanish gobbled up everything else.

A recent episode of the History of England podcast mentioned that the Treaty of Tordesillas in 1493-4 drew a line down the Atlantic about halfway between the islands of Cape Verde and the islands that Columbus had discovered. The Spanish got to keep any non-christian lands to the west of that line and the Portuguese got to keep any non-christian lands to the east of it.

Even though the pope was involved with the treaty, no one outside of Spain and Portugal paid much attention to it.

It isn’t known if the Portuguese knew at the time of the treaty that there was a lump of land straddling that line to the south but they certainly knew about it afterward. The Portuguese found it and started speaking Portuguese all over it.