This study concerns a racial massacre which took place in East St Louis, Illinois on 2 July 1917. The violence erupted during a period of acute industrial unrest, and after significant black migration to the city from the South. These contexts were a focus for Elliott Rudwick's Race Riot, published in 1964, the classic study on this subject. A new approach to the context of industrial conflict is taken in the present work, one which considers the precise timing of the outbreak, and the significance of rumour in the riot. The context of community change is also reconsidered, and the underlying causes of whites' racial hostility are discussed. Close attention is given to the moment of the massacre, and an approach is taken to the social psychology of the collective behaviour of the rioters in order to offer explanations for how an entire community became involved in these atrocities.