The eighteen-year-old Isabella, heir to the King of Castile married her cousin Ferdinand, the heir to the King of Aragon. Ferdinand was seventeen.

Ferdinand became the King of Aragon, and as his wife Isabella was a princess of Castile, two of the most powerful Christain states in Spain were united. At this time the Iberian peninsula was divided into five areas, Portugal on the west coast, Granada on the south coast, Navarre on the north coast, Aragon on the east coast and taking most of the centre was Castile. Castile and Aragon were the largest of the five.

This treaty signed between Portugal and Castile marked the end of the war over the succession to the throne of Castile. Alphonso of Portugal gave up his claim of the throne of Castile and not to marry Joanna of Castile. Joanna agreed to become a nun and remain in Portugal. In return Isabella of Castile gave up claims to some territories that Portugal had claims to. Isabella also pardoned those nobles in Castile that had supported Joanna and Alphonso.

The end of the siege of Granada was marked by the signing of the Treaty of Granada by Ferdinand and Isabella of Castile and Boabdil the sultan of Granada. This treaty ended the Moorish rule of Granada and its transfer to Spanish rule. The actual transfer was delayed until early 1492.

Ferdinand of Spain abolishes the empire of the Moors in Spain when he enters Granada. The Treaty of Granada granted the Muslims in Granada the rights to exercise their own religion and have their own laws.

Ferdinand of Spain demanded that al the Jews in Spain either convert to Christianity or leave the county. This created a huge exodus of people from Spain taking their wealth and skills with them.

Christopher Columbus signed an agreement with Ferdinand and Isabella, the King and Queen of Spain, He specified that he should be given ten percent of any materials that he found on his explorations, for example spices, gems, gold and silver. He also specified that he would fund one eighth of the expedition if in return he received an eighth of the profits. He also wanted to be made Viceroy of all lands that he discovered. ¹

At Venice it was decided to put a force together to remove King Charles of France from Italy. It was signed by the Pope, Ferdinand of Aragon, Maximilian the Holy Roman Emperor, the Ruler of Milan and also had the backing of Venice itself. ¹

The secret treaty signed by Loius XIII of France and Ferdinand II of Aragon who agreed to both invade Naples and remove King Frederick from power. Once it had been captured it was agreed that Italy was to divided between France and Spain.

At a meeting at Calais the terms of the marriage bewteen Arthur, Prince of Wales and Catherine of Aragon were finally agreed.

When Isabella of Castile died many of her children were also dead. The rule of Castile passed to Joanna her eldest surviving daughter. But Joanna's mental state was in question and Isabella had stated in her will that Ferdinand her husband would act a regent if Joanna was unable to rule.

Pope Julius II gave permission for the marriage between Catherine of Aragon and King Henry VIII. The legality of the marriage was in question because Catherine had been married to Henry's elder brother Arthur.

When Ferdinand died, he was succeeded by his daughter Joanna. Joanna's mental state was poor and her son Charles became ruler on her behalf.