Isabella (Civ4)/Civilopedia

Isabella was the daughter of King John II of Castile. At the time of her birth, Spain was divided into a number of smaller kingdoms, with Castile, Portugal and Aragon being three of the largest. The southern part of the country was under Arab rule, the "Moors" having conquered much of Spain in the 8th Century. For Christian Spain, there were two major objectives: unite the country and drive out the Moors. Isabella accomplished both.
After her father's death, Castile was ruled by Isabella's older brother, King Henry IV. At eighteen, and against her brother's express wishes, Isabella married Prince Ferdinand, heir to the throne of Aragon. Henry was furious at her - he had wanted her to marry the King of Portugal - but eventually he forgave her and made Isabella his heir. Upon his death in 1474, Isabella became Queen of Castile, and, after a brief war, made an alliance with Portugal, thus uniting much of Spain.
Isabella and Ferdinand worked surprisingly well together. They co-ruled their two kingdoms equally (according to many historians, Isabella was the better ruler of the two).
Once they were enthroned, the couple set about weakening the Spanish nobility, which Isabella believed had become overly powerful. They created a special military force known as the "Holy Brotherhood" for the express purpose of protecting people and property from attacks by the nobility. They also redistributed some of the nobles' lands and destroyed several of their castles. In other internal matters, Isabella and Ferdinand reorganized the courts and the justice system, and they more closely regulated the country's coinage.
Some of Isabella and Ferdinand's other programs were less appealing. The two rulers were Catholic zealots and they had a rabid hatred for non-Catholics, and especially for Jews. In 1478 they petitioned the Pope to establish the Spanish Inquisition. Under Chief Inquisitor Torquemada, the Inquisition tortured and murdered thousands across Spain, driving the heretics out of the country or underground, or forcing them to convert to Catholicism.
Interestingly, when they conquered Granada, the last Muslim stronghold in Spain, Isabella and Ferdinand treated those Muslims quite well, allowing them to freely practice their religion in Spain. The Jews of Granada, however, were treated as barbarously as their cousins in other parts of Spain.
Perhaps Isabella's most famous act as monarch was her decision to fund Columbus's voyages of exploration. Christopher Columbus was an Italian navigator who was looking for a western route to India; after getting Isabella's backing, he set out to cross the Atlantic to find Asia. Instead, Columbus discovered America.
As a ruler, her record is mixed. She did unite her country along with the help of her husband, Ferdinand. She did drive out foreign powers who had occupied Spain for 700 years. She did bring peace and stability to Spain. She did fund exploration which would bring vast new territory and vast wealth to her kingdom. On the other hand, she did launch a terrible campaign of torture and murder against the most vulnerable population in her lands. To her Christian subjects, then, Isabella probably was the best thing that had ever come their way. However her Jewish subjects probably had a somewhat less positive opinion of Her Majesty. Isabella died in 1504, leaving the kingdom to her daughter.