The key document signed in 1492 that began Spanish colonization in the New World was the Treaty of Tordesillas. Although often associated with Columbus's voyages, the Treaty divided newly discovered lands between Spain and Portugal in a north-south line, allowing Spain to claim vast territories in the Americas. This agreement, endorsed by the Pope, aimed to resolve disputes over colonization and exploration efforts. Subsequent Spanish expeditions led to the establishment of colonies and significant cultural, social, and economic impacts on Indigenous populations, setting the stage for centuries of European dominance in the New World.