In 1900, Chicago made its river flow backward to keep sewage out of Lake Michigan, redirecting the water toward the Mississippi Basin instead

Chicago reversed its river flow in the late 1800s to protect its drinking water. This engineering feat sent waste away from Lake Michigan and into the Mississippi River. However, this connection later allowed invasive species to move between river systems. Asian carp now threaten the Great Lakes, posing a modern ecological problem. This historical project highlights the trade-offs inherent in solving public health emergencies.