Castile.
No region has had as much impact on the history of Spain as Castile, although its appearance as a kingdom on the Spanish stage was later than that of Asturias, León, Navarre or the county of Barcelona (later Catalonia). “Castile made Spain,” claimed the 20th-century philosopher, Ortega y Gasset, although he added that it also “unmade” Spain.
Castile’s impact spread, also, to Latin America where Castilian institutions and language were imposed on native populations. As a result, Castilian, is a major world language and first language of an estimated 350.000.000 speakers** (making it second only to Mandarin in terms of native speakers).
Since the 17th century, Castile’s historical tendency to centralize has not always endeared it to other regions of Spain, notably Catalonia, Valencia, Euskadi (the Basque provinces) and Galicia, all coastal areas with their own languages. People in those regions might admit to speaking “Spanish,” but few will acknowledge that they speak “Castilian.”
Like Aragón, the other major player in medieval Spanish history, Castile became a kingdom in 1035, but it had already made its presence felt as a county (condado) at least a century earlier. Let’s go back and see how Castile came into being.
Castile: The Beginnings.
Up to the beginning of the 10th century, the kingdom of Asturias, protected by the Cantabrian mountains, was the dominant force in the north and west. On the north east coast, the county of Barcelona emerged as a powerful presence in the 9th century under the guidance of Guifré el Pilós (ca. 840-897; in English, Wilfrid the Hairy).
As Asturias gradually moved south of the Cantabrian mountains and spread both east and westwards, it encouraged pioneer settlements as a strategy for expansion and to regain territory lost under the lightning Muslim advance between 711 and 720.
As early as 800, the area between the upper reaches of the Duero and Ebro rivers was known as Castella because of its numerous fortifications built to defend against the Muslims of al-Andalus. In 910, the ancient Roman town of León –south of the Cantabrians– became capital, prompting a change in the name of the kingdom, from Asturias to León.
The kings of León followed the same expansionist strategies as their Asturian predecessors, offering settlers incentives: a substantial degree of liberty in governing themselves in open council and a very real opportunity to acquire land and get rich.
It was a slow and haphazard process, but gradually around the fortifications grew small, mostly self-governing municipalities with their own grants or charters (fueros). These municipalities were peopled by hardy, adventurous individuals whose character was molded by the constant threat of Muslim attacks.

The kings of León delegated control of these repopulated areas or counties (condados) to representatives called counts. Dynastic dissension in León in the mid-10th century allowed one of the counts of Castella, Fernán González, to act increasingly on his own initiative.
Supported by the people, who felt greater loyalty to their local lord than to some distant monarch, Fernán González soon accumulated sufficient power –by simply taking over smaller counties– to act independently of León. For twenty years, from 950-970, he governed the county of Castile, fending off attacks from León and Navarre as well as al-Andalus, while at the same time involving himself in the politics of those Christian kingdoms and the caliphate of Abd al-Rahman III.
Although not as famous as the Cid, Castile’s great hero, Fernán González is viewed historically as the founder of Castile, with a status similar to that of Wilfrid the Hairy who was fundamental in the creation Catalonia. Fernán González’s fame soon achieved legendary standing and his deeds were recounted in the mid 13th-century epic Poema de Fernán González.
Little is known of Fernán González’s early life. He was born ca. 910, son of Count Gonzalo Fernández, and grew up in the Castle of Lara (south east of Burgos). In 929, he appears in documents as Count of Lara and in 932 as Count of Castile. In 939, he helped his lord, King Ramiro II of León, defeat Abd al-Rahman III’s army at Simancas, and on his own initiative resettled the town of Sepúlveda in 940. He even granted the town a charter (fuero), a right normally exercised by the king alone.
Fernán González’s star dimmed for a time after he rebelled against Ramiro in 943-4 and was imprisoned. But such was Fernán’s power and Ramiro’s need to defend against the attacks of Abd al-Rahman III that Ramiro saw it expedient not only to release Fernán but also seek to gain his loyalty by marrying his son and heir, Ordoño, to Fernán’s daughter, Urraca.
Following the death of Ramiro II in 951, León experienced a dynastic struggle which Fernán González used to his advantage. He joined a conspiracy with King García Sánchez I of Navarre to support the claims of Ramiro’s younger son, Sancho (I, el Craso/the Fat), against his own son-in-law, Ordoño III.
Intermarriage, multiple marriages and similarity of names** now complicate the picture enormously, but we needn’t get lost in the labyrinth.
was married not only to Ordoño III but also to
Ordoño IV, and then to Sancho II of Navarre. Fernán’s
second wife was also named Urraca, daughter of King
García Sánchez I of Navarre (his first wife was Sancha,
sister of the same García Sánchez I of Navarre). Three
kings of Navarre are called Sancho Garcés; in León
there are four Ordoños, three Ramiros and a Sancho.
And we could go on!
What is most important is that Fernán González succeeded in unifying under his control numerous counties that until then had acted separately. Although technically still subservient to León, Castile under Fernán González was to all intents and purposes an independent state and a significant force in the ongoing conflicts between León, Navarre and al-Andalus.
The degree of independence Castile now enjoyed can be seen in the establishment of a hereditary line to follow on Fernán’s death (in 970). It was a line that survived until 1028 when Castile was absorbed by its expansionist neighbour Navarre under its energetic king, Sancho Garces III (aka Sancho the Great, r 1000-1035).
The future of Castile as a political entity might well have ended at this point but for issues of inheritance. When Sancho died in 1035 he had arranged for his kingdom to be divided amongst his three sons. The oldest, García, received Navarre and the two younger, Fernando and Ramiro, were given Castile and Aragón respectively.
The important point here is that Castile and Aragón were no longer minor players but were elevated to kingdoms. It is an ironic twist that a king of Navarre, by splitting up his kingdom, should condemn Navarre to a limited future at the same time that he “created” the two kingdoms that were to have the greatest impact on Spain’s destiny.

Coincidentally, Castile and Aragón made their first appearance as kingdoms just after the caliphate of Córdoba broke up (in 1031) into numerous taifa kingdoms. The paths of Castile and Aragón soon diverged, Castile looking south and west, Aragón moving to the east and uniting with the county of Barcelona.
In the late 15th century Castile and Aragón were united under the famous Catholic monarchs, Ferdinand and Isabel, to create the modern unitary country of Spain. Navarre, enclosed between the two newer but increasingly stronger kingdoms, soon lost its early advantage and receded to secondary status.
Of course, Sancho could not foresee any of this, nor could he know that his second son Fernando, first king of Castile (r. 1035-1065), would quickly impose his authority over León and later deprive García of a good chunk of Navarre (La Rioja). Castile was on the march, although at this moment León was still the senior kingdom and Ferdinand seemed to happy to adopt the title of king of León as well as of Castile.
Sources:
Barton, Simon A History of Spain 2nd. ed. Basingstock, Hampshire 2009.
Collins, Roger Early Medieval Spain: Unity in Diversity 2nd. ed. Basingstoke, Hampshire 1995.
Fletcher, Richard The Quest for the Cid London 1989
“ Moorish Spain London 1992
Lomax, Derek W. La Reconquista Barcelona 1984
Phillips, William D. and Carla Rahn A Concise History of Spain Cambridge 2010.
Second map is from http://commons.wikimedia.org/wiki/Maps_of_Spain