Missouri v. Illinois

Background

A State (Missouri) sued to stop Chicago and its Sanitary District from sending sewage through a man-made canal into the Desplaines River, which flows into the Illinois River and then the Mississippi. Missouri alleged the outflow would send about fifteen hundred tons of poisonous filth daily into the Mississippi, pollute riverbed areas belonging to Missouri, and make the water unsafe for drinking, farming, and manufacturing for cities and towns that rely on it. The defendants said the canal mixes Chicago sewage with large amounts of Lake Michigan water and that the Illinois River has actually improved in visible cleanliness.

Reasoning

The Court examined whether it should intervene between States and then reviewed the factual proof. Scientific witnesses sharply disagreed: some experiments with a test bacterium sometimes found traces at the St. Louis intake weeks after release, while other tests showed typhoid germs surviving only a few days. The Court noted heavy dilution from Lake Michigan, disputed chemical and bacterial evidence, and that many towns (including some in Missouri) discharge into the rivers. Because the evidence was conflicting and did not clearly show a present, serious injury to Missouri, the Court concluded the proof was insufficient.

Real world impact

The immediate result is that the Court dismissed Missouri’s bill without prejudice, so the canal and Chicago’s discharge could continue for now. The opinion signals that cities below should consider preventive measures like filtration, and that the High Court will require clear, strong proof before stopping State engineering projects that affect major rivers. Missouri may bring another suit if it can produce more convincing evidence.