The union of unions – over 50 both national and international – represent some 11 million workers across industries both blue and white collar. Theirs is a loose confederation – the AFL has no power to compel its members into any action, although it does arbitrate disputes – but a strong one when running political campaigns and get-out-the-vote efforts. The journey for both the American Federation of Labor and the Congress of Industrial relations from separate and sometimes estranged organizations into a single entity was long and fraught with difficulties, but one that made them stronger than the sum of their parts.

On this day, December 5, in 1955, after 20 years of opposition, the AFL merged with the CIO. The split between the two had come as a result of the industrialization that left industrial workers a fundamentally different constituency, with different skills and needs, than their craftsmen brethren.

The AFL had arisen from the May Day Haymarket riots in Chicago, and the venerable organization secured basic workers rights like limits on work hours, worker safety, and better pay. The CIO, which represented the industrial workers, pursued a less conservative, more confrontational policies, but against the same government opponents as the AFL. The differences between the two were soon overcome by their common goals.