The Chicago River Reversal of 1900: Separating Myth from Measured Impact on Public Health

The reversal of the Chicago River in 1900 is often credited with dramatically lowering mortality by eliminating sewage from the city's drinking water. Contemporary accounts and historians have described it as ending Chicago's typhoid crisis. Using ward-level mortality records and synthetic control methods, I find the immediate effects were more modest than claimed. The reversal reduced mortality by 4% (approximately 985 lives) in 1900, with effects concentrated in summer months consistent with reductions in waterborne disease. These results suggest Chicago's dramatic mortality decline required complementary interventions to produce the dramatic reductions in mortality that were observed in the 1900s. This iconic case highlights that public health progress depends on layered measures rather than single "silver bullet" solutions.