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Why is May Day connected to the Haymarket Affair?

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Red anarchy symbol, a capital letter A inside a circle, painted with rough brush strokes on a white background. — anarchism The “circle-A,” a common anarchist symbol.

May Day is connected to the Haymarket Affair because the 1889 Second International—a federation of socialist parties and unions—designated May 1 as International Workers’ Day to commemorate the events in Chicago.123

The connection stems from a nationwide campaign for an eight-hour workday, which included a call for a mass strike beginning on May 1, 1886. In Chicago, this movement led to a violent confrontation at Haymarket Square on May 4, 1886, where a bomb was thrown during a protest against police brutality, resulting in deaths among both police and civilians.43

Following the incident, several anarchist labor leaders were convicted and executed in a trial later widely condemned as unfair. For generations of activists, these individuals became symbols and martyrs of the international struggle for workers' rights. Consequently, May Day serves as a global observance honoring the historic sacrifices and gains of the labor movement.413