The Louisville was a case heard by the United States Supreme Court in 1895. The case involved a dispute between the Louisville and Nashville Railroad Company and the City of Louisville, Kentucky. The City of Louisville had passed an ordinance that required the railroad company to pay a certain amount of money for the use of the city's streets and alleys. The railroad company argued that the ordinance was unconstitutional because it violated the Fourteenth Amendment's Equal Protection Clause. The Supreme Court held that the ordinance was unconstitutional because it violated the Equal Protection Clause. The Court reasoned that the ordinance was not based on any rational basis and was instead based on the arbitrary and capricious whims of the City of Louisville. The Court also held that the ordinance was not a valid exercise of the City's police power because it did not promote the public health, safety, or welfare. The Court's decision in The Louisville was an important precedent in the development of the Equal Protection Clause. The Court's decision established that the Equal Protection Clause applies to state and local governments, and that laws must be based on a rational basis in order to be constitutional. The Court's decision also established that the police power of a state or local government must be used to promote the public health, safety, or welfare in order to be valid.

In the case of Louisville, the Supreme Court was tasked with determining whether a state could impose taxes on interstate commerce. The majority opinion held that states were not allowed to tax goods or services that crossed their borders, as this would interfere with Congress’s power to regulate interstate commerce. Justice Field dissented from this ruling and argued that while Congress had exclusive authority over regulating interstate commerce, it did not have exclusive authority over taxing it. He reasoned that if states were prohibited from imposing taxes on such activities then they would be unable to raise revenue for public purposes and thus be deprived of an important source of income necessary for providing essential services like education and infrastructure maintenance. Furthermore, he noted that allowing each state to determine its own taxation policies regarding interstate trade would create uniformity in taxation across all states which is beneficial both economically and politically.