By the second World War, the felt industry grew in Portugal, and during the 1940s the production of fur and felt production was centralized in the factories of the municipality, with the establishment of the "Cortadoria Nacional do Pêlo", which was nationalized in 1945. In 1946, 1775 people worked in the hat-making industrial in Portugal, while 1212 were located in São João da Madeira. The activity of this industry was later immortalized by João da Silva Correia, in his romance ""Unhas Negras"", a pejorative reference to the works who worked the open cauldrons that darken and destroyed their fingernails ("unhas negras"literally means "darken/blacken fingernails"). The term was later generally used to identify the citizenry of the municipality. The use of the word "Labor", on the coat-of-arms of the municipality, was intended to signify the importance of these workers in the development of the region. Regardless, the hat-making industries slowly declined in the following decades, with the decline in the use of hats, and the shoe-making industry grew in importance, resulting in its reference as the ""Capital of Footwear"" in Portugal ().