International Workers'/Labours Day (also known as May Day) is a celebration of the international labour movement and left-wing movements. It commonly sees organized street demonstrations and marches by working people and their labour unions throughout most of the world. May 1 is a national holiday in more than 80 countries. It is also celebrated unofficially in many other countries.
United States of America 3 cent Postage Stamp Commemorating Labor Day - Issued 1956