ISABELLA the Catholic, queen of CASTILE. –
B. 22 April 1451 at Madrigal de las Altas Torres,
d. 26 November 1504 at Medina del Campo.
Daughter of Giovanni 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
reigned in Castile, I. was crowned queen in 1474. As soon
as she ascended the throne, she found herself involved in
a war against Alfonso V of Portugal, who supported the
succession to the Kingdom of Castile of his niece Joanna
la Beltraneja, the illegitimate daughter of Henry IV’s wife,
Joanna of Portugal. By the Treaty of Trujillo (1479), I.
obtained from Alfonso V the renunciation, on the part of
his niece, of her alleged rights to Castile. In the same year,
upon the death of Giovanni II of Aragon, Ferdinand succeeded
him in the Kingdom, and the union of the two crowns of
Castile and Aragon opened the way to the unification of
Spain, which I. and Ferdinand partly achieved during their
joint reign, after a long war, through the conquest of the
Muslim Kingdom of Granada (1492). I. also strengthened
the royal authority internally, which had greatly declined
during the reign of Henry IV. Another fundamental concern
of I. was the reform of the regular and secular clergy and
the achievement of the religious unity of the territories under
her authority. New impetus was given to the Inquisition, and
steps were taken toward the assimilation of the Moors and
the Jews, the latter of whom were required either to be
baptized or to leave Spain within four months (edict of
31 March 1492).