Languages of Catalonia
The main cause of Spanish and Catalan social bilingualism in modern Catalonia was large-scale migration from the rest of Spain during the 20th century, as Catalonia started a significant industrialization which demanded an increased workforce from elsewhere. Spanish has historically been spoken among a minority of civil servants born in other regions in Spain and among segments of the wealthiest bourgeoisie. Spanish has also been spoken as a second language by most Catalans, as it has been the only official language over long periods since the eighteenth century.
Northern Catalonia
Northern Catalonia ( , also known as "Catalunya Nord" ), French Catalonia or Roussillon refers to the Catalan-speaking and Catalan-culture territory ceded to France by Spain through the signing of the Treaty of the Pyrenees in 1659 in exchange of France's effective renunciation on the formal protection given to the recent founded Catalan Republic. The area corresponds exactly to the modern French "département" of the Pyrénées-Orientales which were historically part of Catalonia since the old County of Barcelona, and lasted during the times of the Crown of Aragon and the Principality of Catalonia until they were given to France by Spain.