 After the union of the central peninsular Kingdom of Castile with the eastern peninsular Kingdom of Aragon in the 15th century under the Catholic Monarchs in 1492, only Navarra and Portugal were left to complete the whole peninsula under one monarchy.Navarre followed soon after in 1512, and Portugal, after over 400 years as an independent and sovereign nation, in 1580.During this time, the concept of Spain was still unchanged.