Spain was formed in 1469 with the marriage of Isabella I of Castile and Ferdinand II of what other Iberian kingdom?

The answer is Aragon because Ferdinand II of Aragon married Isabella I of Castile in 1469, which led to the formation of Spain. The union between these two powerful Iberian kingdoms brought together their respective territories, resources, and influence, creating a strong and unified nation that would later play a significant role in European history.