Enrique IV was the king of Castile and he had one child to whom the throne could be passed. Unfortunately, his wife had been unfaithful within their marriage and her child, Joanna, was not regarded to be Enrique’s. The nobles would not allow him to pass the throne to an illegitimate child so they encouraged him to pass it to his brother, Don Alfonso. When he would not comply, they attempted to force him to give power to his brother because they felt his wife’s child was not worthy of the throne. They were about to force this change in power when Don Alfonso died. The nobles then turned to Isabella, Enrique and Don Alfonso’s half-sister. Isabella would not forcibly take the throne because she respected authority. She explained the wants and needs of the people to Enrique IV and convinced him to hand her the throne of Castile. Isabella then became Isabella I who controlled all of Castile (Mariejol 30-37).
Isabella I was the person who created court life in Spain. She was known to make sure that the best men and women surrounded her and she made sure that she always appeared dressed as a powerful queen. Her court, as the courts before her, traveled around the kingdom because there was no established capital. She would name people to the aristocracy that were powerful and give them invitations into her court. While many people thought that Isabella I was being frivolous holding court, it allowed her to keep a close watch on the powerful people of Spain. Through having the important nobles and aristocracy in her court, she was able to improve her appearance as a powerful queen and she was able to keep watch on those with power and keep them in check (Mariejol 37). She married Fedinand of Aragón in 1469 and they ruled as partners that were known as the Catholic Monarchs for the rest of Isabella's reign.

Mariejol, Jean H. The Spain of Ferdinand and Isabella. Rutgers University Press:New Jersey. 1961