Isabella I of Castile (1451-1504) was a significant monarch in Spanish history. She became Queen of Castile in 1474 and is best known for her marriage to Ferdinand II of Aragon, which united two of the largest kingdoms in Spain. Together, they completed the Reconquista by capturing Granada in 1492, marking the end of Muslim rule in the Iberian Peninsula.
Isabella's reign also saw the establishment of the Spanish Inquisition and the sponsorship of Christopher Columbus's 1492 voyage, which led to the discovery of the Americas. Her efforts laid the foundation for the unification of Spain and its emergence as a global power.