One of the most significant dates during the reign of the Catholic Monarchs was 12th October 1492: the discovery of America by Christopher Columbus.
The fact that Christopher Columbus (who was not originally Spanish) appealed to a foreign court to offer his services proved that the discovery of America was not incidental.
Portugal and Castilla (Spain) were well-advanced in the exploration of overseas mercantile routes and Sevilla, a wealthy and populous Spanish city, was by then an important commercial centre. We know that the African routes were closed to Castilla in favour of Portugal, In 1479, under the Treaty of Alcacoba, Alfonso V of Portugal renounced his claims to Castilla and recognized the rights of Castilla over the Canary Islands, while Castilla recognized the rights of Portugal over the Azores, Cape Verde and Madeira.
The Canary Islands were an excellent bridgehead for alternate routes. This is what Christopher Columbus offered and he offered it to a State that needed them, but which was also accustomed to and prepared for this type of venture. Unified Spain possessed in 1492 a powerful war machine, a solid economy, an exterior projection, naval experience including the exploration of trade routes and notable scientific-technical potential mathematicians, geographers, astronomers and shipbuilders who had been formed in a melting-pot of three cultures (Jews, Muslims and Christians). Its only rival was its neighbour, Portugal, which, as we know, had put a stop to Spanish expansion in Africa.
Columbus' offer was rapidly accepted in spite of his acknowledged errors. But during his journey to Asia his caravels unexpectedly came across the American continent.
The Spanish were especially well prepared by history to conquer, occupy, populate and exploit new lands and assimilate new people. America thus became the new frontier-land for those people used to its ways and with the military, diplomats and administrative arms at their disposal to face the challenge. By the middle of the 16th century, they had settled in the two most important viceroyalties, Mexico on the Atlantic, and Peru on the Pacific.