In the late 15th century, the Age of Exploration was gathering momentum, with Spain and Portugal at the forefront. Both nations were eager to expand their territories and influence in newly discovered lands. Conflicts arose over claims to these territories, prompting the need for a clear demarcation of spheres of influence. The Treaty of Tordesillas was negotiated in 1494, under the auspices of Pope Alexander VI, who sought to prevent warfare between the two Catholic nations. The treaty established a line of demarcation, designed to end the disputes over newly discovered lands, effectively splitting the New World between Spain and Portugal. After its signing in June, Spain formally ratified the treaty in July to ensure its force and legitimacy.

The treaty had profound implications for the colonization of the Americas and the control of trade routes. Spain's claims to territories in the Americas grew significantly, leading to extensive exploration and the establishment of colonies. The Portuguese, while left with Brazil, also benefited from their rights to Africa and Asia. Over time, European powers would challenge the treaty, leading to further conflicts and the eventual reshaping of colonial boundaries.

However, the Treaty of Tordesillas was not universally accepted, and as other European nations became interested in exploration, they often disregarded the agreement. This disregard culminated in increased tensions and competition for overseas territories. The divvying up of the New World led to the expansion of European influence and the beginning of an era of colonization that would alter the cultural and demographic landscape of the Americas dramatically.