Queen Isabella I of Castile, born in 1451, was a pivotal figure in Spanish history. She is best known for her marriage to King Ferdinand II of Aragon, which united two of the largest kingdoms in Spain and laid the foundation for the modern Spanish state. Together, they sponsored Christopher Columbus's 1492 voyage, leading to the discovery of the Americas. Isabella was also a strong advocate for the Catholic faith, instituting the Spanish Inquisition to maintain religious unity in her realms. Her reign marked the beginning of Spain's rise as a global power, influencing politics, culture, and exploration for centuries to come.