May 1st 1886 labor held a demonstration fighting for an 8 hour work day in Chicago. As the police tried to break up the demonstration someone threw a stick of dynamite at the police. The police opened fire on the crowd. At the end there were 4 dead protesters and 7 dead cops. This is known as the Haymarket massacre.
In 1889 May 1st was chosen as International Worker's day by the Second International to commemorate the Haymarket Massacre and the fight for the 8 hour workday.
U.S. resistance to celebrate International Labor Day — also called International Workers' Day — in May stems from a resistance to emboldening worldwide working-class unity, historians say. This is why they picked to have it in September.
Happy labor day to everyone. I am going to celebrate every May 1st for labor as well.