Labor Day was first celebrated in 1882 in New York City. The idea of a workingman's holiday spread quickly throughout the country as the labor movement grew, and in 1894 Labor Day became a national holiday, celebrated on the first Monday in September.
Most of the rest of the world celebrates May 1 as a day dedicated to workers.
The International Labor Organization is the UN specialized agency which works to protect workers' rights throughout the world. Founded in 1919, it is the only surviving major creation of the Treaty of Versailles which created the League of Nations.
See Also: Workers' Day - May 1