The Herrin massacre took place on June 21–22, 1922 in Herrin, Illinois, in a coal mining area during a nationwide strike by the United Mineworkers of America (UMWA). Although the owner of the mine originally agreed with the union to observe the strike, when the price of coal went up, he hired non-union workers to produce and ship out coal, as he had high debt in start-up costs. After an exchange of gunfire by armed guards and union miners, three miners and 20 non-miners were killed, including the superintendent and 19 strikebreakers.