“The History of the Reign of Ferdinand and Isabella the Catholic” in 3 volumes is one of the best-known works by the American historian William Hickling Prescott. Isabella I (1451–1504) was Queen of Castile from 1474 and Queen consort of Aragon from 1479, reigning over a dynastically unified Spain jointly with her husband Ferdinand II (1452–1516). After a struggle to claim her right to the throne, she reorganized the governmental system, brought the crime rate to the lowest it had been in years, and unburdened the kingdom of the enormous debt her brother had left behind. Isabella's marriage to Ferdinand in 1469 created the basis of the de facto unification of Spain. Isabella and Ferdinand are known for completing the Reconquista, ordering conversion or exile to their Jewish and Muslim subjects, and for supporting and financing Christopher Columbus's 1492 voyage that led to the opening of the New World and to the establishment of Spain as a major power in Europe and much of the world for more than a century.