Previously an eastern county of the kingdom of León, Castile in the 11th century became an independent realm with its capital at Burgos and later Valladolid, and the leading force in the northern Christian states' 400-year Reconquista ("reconquest") of central and southern Spain from the Muslim rulers who had dominated the peninsula since the 8th century.
See list of Kings of Castile.
The capture of Toledo in 1085 added New Castile to the crown's territories, and the battle of Las Navas de Tolosa (1212) heralded the Muslim loss of most of the south. León was finally reunited with Castile in 1230, and the following decades saw the capture of Córdoba (1236), Murcia (1243) and Seville (1248).
The dynastic union of Castile and Aragón in 1469, when Ferdinand II of Aragon wed Isabella I of Castile, led to the formal creation of Spain as a single entity in 1516. See List of Spanish monarchs and Kings of Spain family tree.
The language of Castile emerged as the primary language of Spain - known to many of its speakers as castellano and in English simply as the Spanish language.