All the aspects of the life and times of Queen Isabel I of Castile discussed in this volume would not have been quite so important in world history but for the overriding fact that Isabel was responsible for the projection of Castile into the Americas, thus creating a European connection with the western hemisphere. In this essay, I examine the role Isabel played in the opening of the Atlantic through the lens of her Portuguese connections.

Castile might well have embarked on its American venture if Isabel had not become queen. Castile and Portugal had Atlantic interests that would probably have led one or the other to the ocean's western shores regardless of who sat on the Castilian throne. On the other hand, Isabel's particular circumstances and attitudes and the Portuguese influences on her life guided the decisions that she made, and those in turn led the early Spanish empire to unfold and develop as it did.

That Isabel was strongly influential in the early establishment of the empire is well known and appears in almost every textbook. Nonetheless, there are features of her life that are less well known than they should be and that taken together show that her actions were not improvised, but followed a pattern different from what textbook writers commonly assume.

Queen Isabel could hardly have avoided becoming involved in the increasing Castilian interest in the Atlantic. Her subjects were already actively engaged in maritime ventures, as their ancestors had been for centuries.