Historically, the modern country of Spain was formed in the process known as reconquista. Several independent Christian realms (Asturias, León, Galicia, Castile, Navarre, Aragon, Catalonia) coexisted with the Arab caliphate and had their own identities and borders. Eventually, Castille and Aragon grew in power either through conquest or by dynastic inheritance and merged in 1469 with the marriage of the Catholic Monarchs. After this, the Arab kingdom of Granada was conquered in 1492 and Navarre was merged into the union in 1512 through a combined effort of conquest and collaboration of the local elites. Portugal, formerly part of Leon, gained independence in 1128 and remained independent through all of the reconquista process. These realms sometimes collaborated when they fought against the Arabs. This common enemy is usually considered a crucial catalyst in the union of the different Christian realms.
Since the reign of Phillip V, there has been a process of uniformization by the central authorities. Simultaneously, this uniformization has been repelled by some of the local elites that formed their own national consciences based on traditional, historical, linguistical and cultural traits. Some regions, like Navarre and the Basque Country, maintained certain privileges based on their historical rights, while other regions revolted demanding also better conditions (Revolt of the Comuneros, Revolt of the Brotherhoods, Catalan Revolt) .
The nationalism as a movement with significant support appears by the end of the 19th century, coinciding with the loss of the last parts of the Spanish empire, the abolition of privileges, and the high industrial development of some regions in comparison to others. Following the Spanish civil war, the fascist imposition of Spanish as the only official language and the persecution of all remaining historical languages and identities had a major influence in extending the nationalist thoughts.
Since the beginning of the Spanish transition to democracy, after the dictatorship of Francisco Franco, there have been many movements towards more autonomy in certain regions of the country in order to achieve full independence in some cases, and to achieve their own autonomous "community" in others. It is a controversial topic in Spain and references about it can be found almost everyday on the press, specially in the Basque Country and Catalonia.
Currently, the 2 most voted parties in Spain have different views about the topic. The Popular Party supports a more centralized Spain, with an unitary market, and usually doesn't support movements which lead to a greater autonomy of the regions. The PSOE supports a federal state, with greater autonomy of the regions, but is also contrary to the total independence of one of them.
The structure of the article is determined by social support and thoughts of the claims, so that even if there are political parties claiming independence from Spain for Castile, Cantabria, Valencia, Andalusia or Murcia they hardly get any vote and thus do not represent the popular identitary and national sentiment (percentages of nationalist and regionalist votes are given in parentheses according to figures of the elections held at municipality level in May 2007).