While conditions for workers had been a concern through United States history, advocacy for the working class became particularly prominent by the 1930s, as the rise of the Congress of Industrial Organizations (CIO) in 1935 attests.  While the Catholic Church had officially supported organized labor for decades, that support intensified in the 1930s. Pope Leo XIII had expressed support for organized labor in the late nineteenth century, and Pope Pius XI reiterated that commitment with the issuance of the encyclical Quadragesimo Anno in 1931. The Vatican asserted the right for workers to unionize and to earn a “just wage.”

Many Church leaders in the U.S. would enthusiastically embrace Pius XI's statement and begin to ally with unions across the country. The creation of the CIO would be of particular importance, as many in the Church would support, and in some cases join, the organization in order to bring what many leaders termed “social justice” to the working class. Much of the work of the Church in the area of labor would be conducted through the National Catholic Welfare Conference’s Social Action Department (SAD), which would become a fervent supporter of workers' rights during the Great Depression. For the next several decades, the Church would play a critical role in the labor movement, spreading its Christian ideal of “economic democracy” to the working class, as the resources on this site reveal.