The term "Catholic Monarchs" refers to Isabella I of Castile and Ferdinand II of Aragon, who ruled Spain in the late 15th century. Their marriage in 1469 united two of the largest kingdoms in Spain, leading to the unification of the country. They are known for completing the Reconquista by capturing Granada in 1492, which marked the end of Muslim rule in Spain. The Catholic Monarchs also sponsored Christopher Columbus's voyage in 1492, leading to the discovery of the Americas. Their reign is often associated with the establishment of a centralized Spanish state and the promotion of Catholicism as the dominant religion, including the expulsion of Jews and Muslims from Spain.