Kelly v. Pittsburgh is a United States Supreme Court case that was decided in 1881. The case involved a dispute between the City of Pittsburgh and the heirs of a man named John Kelly. Kelly had owned a piece of property in Pittsburgh, and the city had taken it for public use without providing any compensation to the heirs. The heirs sued the city, claiming that the taking of the property was unconstitutional. The Supreme Court ruled in favor of the heirs, finding that the city had violated the Fifth Amendment of the United States Constitution, which states that private property shall not be taken for public use without just compensation. The Court held that the city had not provided the heirs with just compensation for the taking of the property, and thus the taking was unconstitutional. The Court's decision in Kelly v. Pittsburgh established the principle that the government must provide just compensation when it takes private property for public use. This principle has been applied in numerous cases since then, and it remains an important part of the law today.

Justice Field delivered the dissenting opinion in Kelly v. Pittsburgh, arguing that the majority's decision was contrary to established precedent and would lead to a dangerous expansion of municipal power. He argued that municipalities should not be allowed to use their police powers for private gain or benefit, as this could lead to arbitrary and oppressive actions by local governments against citizens who are unable or unwilling to pay exorbitant fees for services they do not need. Furthermore, he noted that there is no legal authority granting cities such broad discretion over matters concerning public health and safety; rather, these decisions must be made by state legislatures or Congress itself. Finally, Justice Field concluded his dissent with an admonition: if cities were given unchecked power in this area it would open up a Pandora's box of potential abuses which could ultimately undermine our system of government based on limited governmental powers and individual rights.