Columbia subject headings:
Labor unions--Political activity--United States--History.
Working class--Political activity--United States.
Working class--United States--History.
Harvard subject headings:
Labor unions--Political activity--United States--History
Working class--United States--History
Working class--United States--Political activity--History.
Princeton subject headings:
Labor unions--Political activity--United States--History.
Working class--United States--Political activity--History.