The Crown of Castile, as a historic entity, is usually considered to have begun in 1230 with the third and definitive union of the two kingdoms of León and Castile, or more concretely, with the union of their parliaments a few decades later. In 1230 Saint Ferdinand III was crowned King of Castile (which included the former kingdom of Toledo) and Leon (which included the Kingdom of Galicia).
The Kingdom of León arose out of the Kingdom of Asturias. The Kingdom of Castile appeared initially as a county of the Kingdom of León. From the second half of the 10th century to the first half of the 11th century it changed hands between Leon and the Kingdom of Navarre. In the 11th century it became a kingdom in its own right.
The kingdoms of Leon and Castile had been united twice previously:
Ferdinand III received the Kingdom of Castile from his mother Berenguela of Castile in 1217, and the Kingdom of León from his father (Alfonse IX of León) in 1230. From then on the two kingdoms were united under the name of the Kingdom of León and Castile, or simply as the Crown of Castile. Ferdinand III later conquered the Guadalquivir Valley, while his son Alfonso X conquered the Kingdom of Murcia from Al-Andalus, further extending the area of the Crown of Castile. Given this, the kings of the Crown of Castile traditionally styled themselves "King of Castile, Leon, Toledo, Galicia, Murcia, Jaén, Cordoba, Seville, and Lord of Biscay and Molina," among other possessions they later gained. The heir to the throne has been titled Prince of Asturias since the 14th century.
Almost immediately after the union of the two kingdoms under Ferdinand III, the parliaments of Castile and León were united. It was divided into three estates, which corresponded with the nobility, the church and the cities, and included representation from Castile, León, Galicia, Toledo, Navarre and the Basque provinces. 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).
Under Alfonso X, most sessions of the Cortes of both kingdoms were held jointly. The Cortes of 1258 in Valladolid comprised representatives of Castile, Extremadura and León ("de Castiella e de Estremadura e de tierra de León") and those of Seville in 1261 of Castile, León and all other kingdoms ("de Castiella e de León e de todos los otros nuestros Regnos"). 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.
Although the individual kingdoms and cities initially retained their individual historical rights—including the Old Fuero of Castile (Viejo Fuero de Castilla) and the different fueros of the municipal councils of Castile, León, Extremadura and Andalucía—a unified legal code for entire new kingdom was created in the Siete Partidas (c. 1265), the Ordenamiento de Alcalá (1248) and the Leyes de Toro (1505). These laws continued to be in force until 1889, when a new Spanish civil code (the Código Civil Español) was enacted.
In the 13th century there were many languages spoken in the Kingdoms of León and Castile among them Castilian, Leonese, Basque and Galician. But throughout the century Castilian gained more and more prominence as the language of culture and communication. One example of this is the 'Cantar de Mio Cid'.
In the last years of the reign of Ferdinand III Castilian began to be used to certain types of documents, such as the Visigothic Code, then the basis of the legal code for Christians living in Muslim Cordova, but it was during the reign of Alfonso X that it became the official language. Henceforth all public documents were written in Castilian, likewise all translations of Arabic legal and government documents were made into Castilian instead of Latin.
Some people think that the substitution of Castilian for Latin was due to the strength of the new language, whereas others consider that it was due to the influence of Hebrew-speaking intellectuals who were hostile towards Latin, the language of the Christian Church.[citation needed]
Furthermore, in the 13th century many Universities were founded like the Leonese Salamanca and the Castilian Estudio General of Palencia were the among the first universities in Europe.
In 1492, under the Catholic Monarchs, the first edition of the Grammar of the Castilian Language by Antonio de Nebrija was published.
On the death of Alfonso XI a dynastic conflict started between his sons, the Infantes Pedro and Henry, Count of Trastámara, which became entangled in the Hundred Years' War. Alfonso XI had married Maria of Portugal with whom he had his heir, the Infante Pedro. However, the King also had many illegitimate children with Eleanor of Guzman, among them the above-mentioned Henry, who disputed Pedro's right to the throne once the latter became king.
In the resulting struggle, in which both brothers claimed to be king, Pedro allied himself with Edward, the Prince of Wales, "the Black Prince." In 1367 the Black Prince defeated Henry II's allies at the Battle of Nájera, restoring Pedro's control of the kingdom. The Black Prince, seeing that the king would not reimburse his expenses, left Castile. Henry, who had fled to France, took advantage of the opportunity and recommenced the fight. Henry finally was victorious in 1369 in the Battle of Montiel, in which he killed Pedro.
In 1371 the brother of the Black Prince, John of Gaunt, 1st Duke of Lancaster, married Constance, Pedro's daughter. In 1388 he claimed the Crown of Castile in the name of his wife, the legitimate heir according to the Cortes de Seville of 1361. He arrived in A Coruña with an army and took the city. He then moved on to occupy Santiago de Compostela, Pontevedra and Vigo. He asked John I, Henry II's son, to give up the throne in favor of Constance.
John declined but proposed that his son, the Infante Henry, marry John of Gaunt's daughter Catherine. The proposal was accepted, and the title Prince of Asturias was created for Henry and Catherine. This brought an end to the dynastic conflict, strengthened the House of Trastámara's position and created peace between England and Castile.
During the reign of Henry III royal power was restored, overshadowing the much powerful Castilian nobility. In his later years Henry delegated some of his power to this brother Ferdinand of Antequera, who would be regent, along with his wife Catherine of Lancaster, during the childhood of this son Prince John. After the Compromise of Caspe in 1412, Ferdinand left Castile to become king of Aragon.
Upon the death of his mother John II, at the age of 14, took to the throne and married his cousin Maria of Aragon. The young king entrusted his government to Álvaro de Luna, the most influential person in court and allied with the lesser nobility, the cities, the clergy and the Jews. This brought together the mutual dislikes of the king shared by the greater Castilian nobility and the Aragonese infantes, sons of Ferdinand of Antequera, who sought to control the Castilian crown. This eventually led to war in 1429 and 1430 between the two kingdoms. Álvaro de Luna won the war and expelled the Aragonese Infantes from Castile.
Henry IV unsuccessfully tried to re-establish the peace with the nobility that his father had shattered. When his second wife, Joan of Portugal, gave birth to Princess 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 Joanna out of the line of succession. After the death of Alfonso in an accident, Henry signed the Treaty of the Bulls of Guisando with his half-sister Isabella in which he named her heiress in return for her marrying a prince chosen by him.
In October 1469 Isabella and Ferdinand, heir to the throne of Aragon, married in secret in the Palacio de los Vivero in Valladolid. The consequence was a dynastic union of the Crown of Castile and Crown of Aragon in 1479 when Ferdinand ascended to the Aragonese throne. This union however was not effective until the reign of his grandson Charles I. Ferdinand and Isabella were related and had married without papal approval. Although Isabella wanted to marry Ferdinand, she refused to proceed with the marriage until she received a papal dispensation. Consequently, Ferdinand's father forged a papal dispensation for the two to marry. Isabella believed that the dispensation was authentic and the marriage went ahead. A genuine papal dispensation arrived afterwards. Later Pope Alexander VI bestowed upon them the title of the Catholic Monarchs.