Labor Day is a United States federal holiday observed on the first Monday in September. It is celebrated as the unofficial end of summer, and the start of the NFL football season. Some fashion-conscious people say it is gauche* to wear white after Labor Day!
*lacking social grace, sensitivity, or acuteness : )
Here’s more history behind it from Wikipedia : The first Labor Day in the United States was observed on September 5, 1882 in New York City, by the Central Labor Union of New York, the nation’s first integrated major trade union. It became a federal holiday in 1894, when, following the deaths of a number of workers at the hands of the U.S. military and U.S. Marshals during the Pullman Strike, President Grover Cleveland put reconciliation with the labor movement as a top political priority. Fearing further conflict, legislation making Labor Day a national holiday was rushed through Congress unanimously and signed into law a mere six days after the end of the strike.
The September date originally chosen by the Central Labor Union (CLU) of New York – and at that time observed by many of the nation’s trade unions for several years – was selected rather than the more widespread May 1 International Workers’ Day because Cleveland was concerned that observance of the latter would stir up negative emotions linked to the Haymarket Affair, for which it had been observed to commemorate.