The "Count of Castile" refers to a noble title in the historical region of Castile, which is now part of modern-day Spain. The title was established during the early Middle Ages and was held by various noble families. The Counts played a significant role in the political and military affairs of the region, especially during the Reconquista, when Christian kingdoms sought to reclaim territory from Muslim rule. The title of Count of Castile eventually evolved into the title of Duke of Castile and was associated with the rise of the Kingdom of Castile. This kingdom became one of the most powerful in Spain, contributing to the unification of the country under the Catholic Monarchs, Ferdinand II of Aragon and Isabella I of Castile.