George Weigel on the Church and the unions :

The defense of nascent trade unionism in late-nineteenth-century America is a bright chapter in the history of the Catholic Church in the United States. When a nervous Vatican was prepared to write off trade unions as the kind of “secret societies” the Church had long opposed, Cardinal James Gibbons of Baltimore defended the Knights of Labor in Rome and forestalled a Vatican condemnation of American unions—an accomplishment that helped the Church retain the loyalty of working class people.