Dean Milk Co. v. City of Madison, Wisconsin, 340 U.S. 349 (1951), was a United States Supreme Court case dealing with the Dormant Commerce Clause. The court held that a municipal ordinance requiring all milk sold in Madison to be pasteurized at an approved plant within 5 miles of the city, unconstitutionally discriminated against interstate commerce. Illinois milk producer, Dean Milk, on appeal from a state court holding that found the municipal ordinance to be reasonable, charged that the true purpose of the ordinance was to protect local industries from competition from non-local producers.