ISABELLA the Catholic, Queen of CASTILE. — B. Apr. 22, 1451 at Madrigal de las Altas Torres; d. Nov. 26, 1504 at Medina del Campo.
Daughter of John II of Castile and Isabella of Portugal, she married Ferdinand of Aragon at Valladolid in 1469. Upon the death of her brother Henry IV, who ruled in Castile, I. was crowned queen in 1474. Scarcely had she ascended the throne when she became embroiled in a war against Alfonso V of Portugal, who upheld the claim of Joanna la Beltraneja, the illegitimate daughter of Henry IV’s wife Joanna of Portugal, to the throne of Castile. By the Treaty of Trujillo (1479) I. secured from Alfonso V the renunciation of his niece’s supposed rights to Castile. In the same year, John II of Aragon having died, Ferdinand succeeded him in the kingdom, and the union of the two crowns of Castile and Aragon paved the way for the unification of Spain, which I. and Ferdinand partly achieved during their joint reign, after a long war, by the conquest of the Muslim Kingdom of Granada (1492). I. also strengthened royal authority within the realm, which had greatly declined during the reign of Henry IV. Another fundamental concern of hers was the reform of both regular and secular clergy and the realization of religious unity in the territories under her authority. New impetus was given to the Inquisition, and the assimilation of Moors and Jews was pursued; the latter were required either to be baptized or to leave Spain within four months (edict of Mar. 31, 1492).