It continued to exist as a separate entity after the personal union in 1469 of the crowns of Castile and Aragon with the marriage of the Catholic Monarchs up to the promulgation of the Nueva Planta decrees by Philip V in 1716.

In the early 18th century, Philip of Bourbon won the War of the Spanish Succession and imposed unification policies over the Crown of Aragon, supporters of their enemies.

It was divided into three estates, which corresponded with the nobility, the church and the cities, and included representation from Castile, León, Galicia, Toledo, and the Basque Provinces.

[citation needed] Initially the number of cities represented in the Cortes varied over the next century, until John I permanently set those that would be allowed to send representatives (procuradores): Burgos, Toledo, León, Sevilla, Córdoba, Murcia, Jaén, Zamora, Segovia, Ávila, Salamanca, Cuenca, Toro, Valladolid, Soria, Madrid and Guadalajara (with Granada added after its conquest in 1492).

Subsequent Cortes were celebrated separately, for example in 1301 that of Castile in Burgos and that of León in Zamora, but the representatives demanded that the parliaments be reunited from then on.

But, as the century progressed, Castilian gained increasing prominence as the language of culture and communication – one example of this is the Cantar de Mio Cid.

[9] On the death of Alfonso XI a dynastic conflict started between his sons, the Infantes Peter (Pedro) and Henry, Count of Trastámara, which became entangled in the Hundred Years' War (between England and France).

In 1367, the Black Prince defeated Henry II's allies at the Battle of Nájera, restoring Pedro's control of the kingdom.

In his later years Henry delegated some of his power to his brother Ferdinand I of Antequera, who would be regent, along with his wife Catherine of Lancaster, during the childhood of his son John II.

The young king entrusted his government to regent Álvaro de Luna, the most influential person in court and allied with the lesser nobility, the cities, the clergy, and the Jews.

When his second wife, Joan of Portugal, gave birth to Infanta Joanna, it was claimed that she was the result of an affair of the Queen with Beltrán de la Cueva, one of the King's chief ministers.

The King, besieged by riots and the demands of the nobles, had to sign a treaty in which he named as his successor his half-brother Alfonso, leaving Infanta Joanna out of the line of succession.

After the death of Alfonso in an accident, Henry IV signed the Treaty of the Bulls of Guisando with his half-sister Isabella I in which he named her heiress in return for her marrying a prince chosen by him.

In October 1469 Isabella I and Ferdinand II, heir to the throne of Aragon, married in secret in the Palacio de los Vivero in Castilian Valladolid.

Despite their titles of "Monarchs of Castile, Leon, Aragon and Sicily" Ferdinand and Isabella reigned over their respective territories, although they also took decisions together.

They also took further measures against the nobility, destroying feudal castles, prohibiting private wars and reducing the power of the Adelantados (a governor-like military office in regions recently conquered).

Also in 1492, the Christopher Columbus maritime expedition claimed the newly found lands in the Americas for the Crown of Castile and began the New World conquests.

Through the Concordia de Villafáfila of 1506, Ferdinand returned to Aragon and Phillip was recognized as King of Castile, with Joanna a co-monarch.

Joanna of Castile and Philip immediately added to their titles the kingdoms of Indies, Islands and Mainland of the Ocean Sea.

Her isolated confinement-imprisonment in the Santa Clara Convent at Tordesillas, to last over forty years until death, began with her father's orders in 1510.

This was partly because he was a foreign-born king (born in Ghent), and even before his arrival in Castile he had granted important positions to Flemish citizens and had used Castilian money to fund his court.

Despite threats, the parliament led by Juan de Zumel representing Burgos, resisted and forced the king to respect the laws of Castile, remove all foreigners from important governmental posts, and learn to speak Castilian.

Charles was conscious of the fact that he had options to become emperor and needed to impose his authority over Castile to gain access to its riches for his imperial goals.

Philip II continued the politics of Charles I, but unlike his father he made Castile the core of the Spanish Empire, centralising all administration in Madrid.

In fact, since the reign of Charles I the financial burden of the empire had fallen mainly on Castile, but under Philip II the cost quadrupled.

That same year Philip ordered the proclamation of the La Pragmática; an act whereby all Moriscos had to abandon all Moorish traditions and become true Catholics.

Faced with the collapse of the Exchequer, in order to maintain the hegemony of Philip IV's Spanish Empire, the Count-Duke of Olivares, the king's favourite (valido) from 1621 to 1643, tried to introduce a series of reforms.

This was in order to alleviate interior conflicts sparked off by his predecessor (revolts in Portugal, Catalonia and Andalusia) and achieve peace in Europe.

Upon the death of Philip IV in 1665, and with the incapacity of Charles II to govern, Spain suffered an economic slowdown and battles for power between the different 'favourites'.

[10][11] North – Septentrional South – Meridional In the viceroyalties the viceroy, whose term etymologically means "in the place of the king", concentrated all public power.