Sos del Rey Católico is a historic town and municipality in the Cinco Villas comarca, province of Zaragoza, in Aragon, Spain.HistoryLocated on rocky and elevated terrain, this important border town served well as a stronghold from the year 907 when it was reclaimed by Sancho I of Pamplona.It was incorporated in 1044 by Ramiro I into the Kingdom of Aragon.In the year 1452, during the War of Navarre, Queen Juana Enríquez de Córdoba moved to the town, then called "Sos". There she gave birth to the infante Ferdinand on March 10, 1452, who later became Ferdinand II of Aragon, one of the Catholic Monarchs. His birth added "d'o Rei Catolico" to the name of the town, which translates as either "You are of the Catholic Monarch" or "You belong to the Catholic Monarch".In 1711 it was named as the capital of the Cinco Villas.