The Kingdom of Castile (/kæˈstiːl/; Spanish: Reino de Castilla: Latin: Regnum Castellae) was a polity in the Iberian Peninsula during the Middle Ages.

It traces its origins to the 9th-century County of Castile (Spanish: Condado de Castilla, Latin: Comitatus Castellae), as an eastern frontier lordship of the Kingdom of León.

[3] In the Al-Andalus chronicles from the Cordoban Caliphate, the oldest sources refer to it as Al-Qila, or "the castled" high plains past the territory of Alava, further south than it and the first encountered in their expeditions from Zaragoza.

The name reflects its origin as a march on the eastern frontier of the Kingdom of Asturias, protected by castles, towers, or castra,[citation needed] in a territory formerly called Bardulia.

The County of Castile, bordered in the south by the northern reaches of the Spanish Sistema Central mountain system, was just north of modern-day Madrid province.

A mix of settlers from the Cantabrian and Basque coastal areas, which were recently swelled with refugees, was led under the protection of Abbot Vitulus and his brother, Count Herwig, as registered in the local charters they signed around the first years of the 800s.

The areas that they settled did not extend far from the Cantabrian southeastern ridges, and not beyond the southern reaches of the high Ebro river valleys and canyon gores.

Sancho III, acting as feudal overlord, appointed his younger son (García's nephew) Ferdinand as Count of Castile, marrying him to his uncle's intended bride, Sancha of León.

Following Sancho's death in 1035, Castile returned to the nominal control of León, but Ferdinand, allying himself with his brother García Sánchez III of Navarre, began a war with his brother-in-law Vermudo.

Sancho later attacked Alfonso VI and invaded León with the help of El Cid, and drove his brother into exile, thereby reuniting the three kingdoms.

Alfonso VII refused his right to conquer the Mediterranean coast for the new union of Aragón with the County of Barcelona (Petronila and Ramón Berenguer IV).

The centuries of Moorish rule had established Castile's high central plateau as a vast sheep pasturage; the fact that the greater part of Spanish sheep-rearing terminology was derived from Arabic underscores the debt.

[14] In addition, he took advantage of the decline of the Almohad empire to conquer the Guadalquivir Valley whilst his son Alfonso X took the taifa of Murcia.

The marriage of Ferdinand II of Aragon and Isabella I of Castile, in 1469 at the Palacio de los Vivero in Valladolid began the familial union of the two kingdoms.

In 1492, the Kingdom of Castile conquered the last Moorish state of Granada, thereby ending Muslim rule in Iberia and completing the Reconquista.

Over time, these assemblies evolved into municipal councils, known as variously as ayuntamientos or cabildos, in which some of the inhabitants, the property-owning heads of households (vecinos), represented the rest.

Due to the increasing power of the municipal councils and the need for communication between these and the King, cortes were established in the Kingdom of León in 1188, and in Castile in 1250.

Unlike other kingdoms, Castile didn't have a permanent capital (neither did Spain until the 16th century), so the cortes were celebrated in whichever city the king chose to stay.

In the earliest Leonese and Castilian Cortes, the inhabitants of the cities (known as "laboratores") formed a small group of the representatives and had no legislative powers, but they were a link between the king and the general population, something that was pioneered by the kingdoms of Castile and León.

During the reign of Alfonso VIII, the king began to use the canting arms of Castile as its emblem, in its blazons and banners, which were gules, a three towered castle or masoned sable and ajouré azure.