The support of the city to the forces of the Republic cost him dearly in Barcelona, not only during the three years of war, but during the thirty-six years of dictatorship (1939-1975). The new regime made a political purge that relegated to any person related to the Republic, communism or Catalan. Many people were forced into exile, while others were imprisoned and some executed, as the Companys President, shot in Montjuïc in 1940 -. The postwar period was a period of great economic hardship, the collapse suffered during the war and the subsequent isolation of the Franco regime internationally. Until the 1950's, with the alliance with the United States and the arrival of Marshall Plan, not revived the economy. Then began a progressive development, embodied in the implementation in the Zona Franca in Barcelona from the SEAT company, the first major car factory built in Spain.
This time it is worth noting that in 1952, Barcelona hosted the XXXV International Eucharistic Congress, which allowed the development of a new neighborhood known as Congrès. Moreover, the years of dictatorship is characterized by urban development, which was the rampant construction of affordable housing to absorb immigration from mainly Spanish communities such as Andalusia, Murcia and Galicia. Housing construction was carried out, in many cases without prior urban planning, and using cheap materials which, over the years, would cause various problems such as aluminosis. The building frenzy caused a notable increase in population and the creation of new neighborhoods, both within the city, including Caramel, Nou Barris, Guinardó, Vall d'Hebron, La Sagrera, Clot, Verneda, Poblenou, etc., as populations adjacent to Barcelona and Hospitalet de Llobregat, Santa Coloma de Gramenet, Sant Adria de Besos or Badalona, which multiplied the demographics of the metropolitan area of Barcelona, also called "girdle".
The increase in population and the emergence of the car in 1960 was forced to develop the Metro, on the one hand, and the massive paved streets, installing traffic lights and construction of the first ring roads of the city. In these years also improved distribution system of running water, sewerage, electricity supply and lighting of the city.
From the cultural point of view, the massive influx of immigration increased the number of Spanish speakers in a city where, until 1930, the Catalan language was clearly the dominant language. It also contributed to the power of new mass media, radio and television, which were issued only in Castilian, and the fact that Castilian was the only language officially recognized by the regime, and therefore only used in public life.
During the last years of the regime began a broad social movement that, while calling for democracy and political amnesty, claiming back the use of Catalan and normalization of Catalan culture. The activity of movements such as Els Setze Jutges (composed by artists such as Raimon, Lluís Llach, Joan Manuel Serrat, etc), created a demand battlefront Catalan nationalist and democratic. At the time, it happened several protest actions, including being held in the convent of the Capuchin Sarrià to be a Democratic Union of Students (1966), the closure in Montserrat in protest against the process of Burgos (1970) or the first Assemblea of Catalunya, on November 7, 1971 in the parish of Saint Augustine. From this came the slogan Assemblea llibertat, amnesty, Statute of Autonomy (freedom, amnesty, statute of autonomy)