The Castilian crown refers to the monarchy that ruled over the historical region of Castile in Spain. It played a significant role in the unification of Spain during the late 15th century, particularly under the reign of Isabella I of Castile and her husband, Ferdinand II of Aragon. Their marriage united the two powerful kingdoms, leading to the establishment of a more centralized Spanish state. The crown was instrumental in the exploration and colonization of the Americas, as it sponsored voyages like that of Christopher Columbus in 1492. The wealth generated from these new territories significantly enhanced the power and influence of the Castilian crown in Europe.