On June 7, 1494, the governments of Spain and Portugal agreed to the Treaty of Tordesillas, named for the city in Spain in which it was created. The Treaty of Tordesillas neatly divided the “New World” of the Americas between the two superpowers.
Spain and Portugal divided the New World by drawing a north-to-south line of demarcation in the Atlantic Ocean, about 100 leagues (555 kilometers or 345 miles) west of the Cape Verde Islands, off the coast of northwestern Africa and then controlled by Portugal. All lands east of that line (about 46 degrees, 37 minutes west) were claimed by Portugal. All lands west of that line were claimed by Spain.
Spain and Portugal adhered to the treaty without major conflict between the two, although the line of demarcation was moved an additional 270 leagues (about 1500 kilometers or 932 miles) farther west in 1506, which enabled Portugal to claim the eastern coast of what is now Brazil.
The results of this treaty are still evident throughout the Americas today. For example, all Latin American nations are predominantly Spanish-speaking countries with the sole exception of Brazil where Portuguese is the national language. This is because the eastern tip of Brazil falls east of the line of demarcation settled upon in the Treaty of Tordesillas, and was where the majority of Portuguese colonization occurred. The borders of modern Brazil have expanded since the 1506 expansion of the Treaty of Tordesillas.
Spain and Portugal were the only signatories of the treaty because at the time, they were the only European powers to establish a presence in the Americas. The treaty did not consider any future claims made by the British, French, and other European superpowers of their respective times. The British, French, and Dutch Empires did not claim parts of the Americas until years after the Treaty of Tordesillas.
More significantly, however, the Treaty of Tordesillas completely ignored the millions of people already living in established communities in the Americas. The treaty stipulated that any lands with a “Christian king” would not be colonized. Of course, by that time, Christianity had not spread broadly in the Americas. This meant that unless the land was already claimed by a Christian (European) ruler, by the terms of their treaty, Spain and Portugal could claim practically any land they managed to conquer in the Americas. The resulting conquest and colonization proved disastrous for civilizations, such as the Inca, Taino, and Aztec, along with thousands of other communities throughout the Americas.