Queen Isabella I of Castile (1451-1504) was a significant figure in Spanish history. She became queen in 1474 and is best known for her marriage to King Ferdinand II of Aragon, which united two of the largest kingdoms in Spain. Together, they completed the Reconquista by capturing Granada in 1492, ending centuries of Muslim rule in the Iberian Peninsula. Isabella is also famous for sponsoring Christopher Columbus's 1492 voyage, which led to the discovery of the Americas. Her reign marked the beginning of Spain's rise as a global power, and she played a crucial role in establishing a unified Spanish state.