Isabella I (1451-1504) was queen of Castile from 1474 to 1504. She and her husband, Ferdinand V, founded the modern Spanish state.
Born in Madrigal on April 22, 1451, Isabella was the daughter of John II of Castile by his second wife, Isabella of Portugal, and was the half sister of Henry IV, who succeeded to the Castilian throne in 1454. Henry had recognized Isabella as his heir over the claims of his daughter Juana, whose royal paternity was questioned by the King's opponents, but when Isabella married Ferdinand of Aragon in 1469, Henry conferred the succession on Juana.
When Henry died in 1474, Isabella immediately claimed the throne. In the ensuing civil war Juana was supported by a cross section of the great nobles as well as by the Portuguese king, Alfonso V. Alfonso's army was defeated at the battle of Toro in 1476, and he made peace with the Catholic Monarchs (as the pair were styled) in 1479. In that same year Ferdinand succeeded to the throne of Aragon, associating Isabella with his rule in 1481. With Juana sequestered in a convent, the crucial step in the formation of a united Spain had been taken.
Although "Spain" in 1481 was little more than a personal union of the two crowns, and remained so during Isabella's lifetime, the ultimate process of unification was facilitated by the achievements of the Catholic Monarchs, the most significant of which was the reconquest of the Peninsula from the Moorish kingdom of Granada. Begun in 1481, the war lasted until 1492, ending in a complete Spanish victory. Generous peace terms, which allowed the inhabitants to retain their Islamic religion and laws, were soon violated, and, following an abortive Moorish revolt in 1502, adult Moslems who refused Christian baptism were expelled from Spain.
Earlier, in 1492-the same year in which Isabella agreed to subsidize Columbus's first voyage—the Catholic Monarchs had ordered the expulsion of all unbaptized Castilian Jews, nearly 150,000 in all. The Inquisition, established at the Monarchs' behest in 1478, was thus offered a free field to uncover and penalize the backslidings of all remaining "New Christians" (baptized Jews and Moors).
Isabella had five children. The marriage of daughter Catherine of Aragon to Henry VIII of England eventually resulted in the controversy leading to the English Reformation; and the marriage of Joanna (Juana) the Mad to Philip of Burgundy, son of the German emperor Maximilian I, produced a successor to the Spanish crown—Charles I of Spain (Charles V of the Holy Roman Empire). Isabella, who died on Nov. 26, 1504, nearly undid the work of the Catholic Monarchs by leaving the Castilian throne, not to Ferdinand, but to her demented daughter.
One of the best biographical histories of the Catholic Monarchs remains William Prescott, History of the Reign of Ferdinand and Isabella (3 vols., 1838; new rev. ed. 1873). A vivid biographical treatment of the royal couple is in Townsend Miller, The Castles and the Crown: Spain, 1451-1555 (1963). □