Isabella I of Castile was a significant monarch in Spanish history, reigning from 1474 until her death in 1504. She is best known for uniting the kingdoms of Castile and Aragon through her marriage to Ferdinand II of Aragon. Together, they completed the Reconquista by conquering Granada, the last Muslim stronghold in Spain, in 1492. Isabella's reign marked the beginning of Spain's rise as a global power. She sponsored Christopher Columbus's 1492 voyage, leading to the discovery of the Americas. Her policies also laid the groundwork for the Spanish Inquisition, which aimed to maintain Catholic orthodoxy in her realms.