Concluded the Treaty of Tordesillas with Portugal, dividing non-European territories between the Spanish and Portuguese crowns.
On 7 June 1494, representatives of Isabella and Ferdinand and of the Portuguese Crown signed the Treaty of Tordesillas. The agreement moved the line of demarcation established by the papal bull Inter caetera and divided newly discovered non-European territories between Spain and Portugal along a meridian west of the Cape Verde Islands.
Under the treaty, lands to the west of the line, including most of the Americas, were assigned to Castile, while territories to the east were reserved for Portugal, shaping patterns of colonization in Brazil, Africa, and Asia. Isabella’s crown thus secured primary claims over vast, then-unmapped regions, laying groundwork for a Spanish American empire.
The Treaty of Tordesillas is historically significant because it formalized an early attempt at global partition by European powers and anchored diplomatic norms concerning exploration, sovereignty, and papal authority.
From the standpoint of women’s history, Isabella’s participation—through her authority as queen of Castile—in negotiating and accepting this treaty exemplifies a woman at the center of decisions about global territorial division and imperial expansion, highlighting her role in the legal and diplomatic architecture of Europe’s overseas empires.