On a sweltering summer Sunday in July 1919, a group of Black teenagers with a makeshift wooden raft unintentionally drifted across an invisible boundary line into an area of Lake Michigan near 29th Street used by white beachgoers. A 24-year-old white man, George Stauber, threw stones at the teens, causing the drowning death of 17-year-old Eugene Williams. His death and a white police officer’s refusal to arrest Stauber lit the fuse on simmering racial hostility that would explode into what historians have called the most violent week in Chicago history. In the end, 38 people were killed (23 of the...