The Reading Railroad Company v. Pennsylvania was a case heard by the United States Supreme Court in 1872. The case centered around the constitutionality of a state freight tax imposed by the state of Pennsylvania. The Reading Railroad Company argued that the tax was unconstitutional because it violated the Commerce Clause of the United States Constitution. The Court ultimately ruled in favor of the state of Pennsylvania, finding that the tax was constitutional. The Court reasoned that the tax was not a burden on interstate commerce, as it was imposed on all freight, regardless of origin or destination. The Court also found that the tax was not discriminatory, as it was imposed on all freight, regardless of the state of origin. The Court further found that the tax was not excessive, as it was based on the value of the freight and not on the number of shipments. Ultimately, the Court found that the tax was constitutional and that the state of Pennsylvania had the right to impose it. The Court's ruling established the precedent that states have the right to impose taxes on freight, so long as the taxes are not discriminatory or excessive. This ruling has been cited in numerous cases since then, and has been used to uphold the constitutionality of state taxes on freight.

In the case of Reading Railroad Company v. Pennsylvania, the Supreme Court was asked to decide whether a state freight tax imposed on interstate commerce violated the Commerce Clause of the United States Constitution. The majority opinion held that it did not violate this clause and upheld the tax as constitutional. However, Justice Field dissented from this decision and argued that such a tax is unconstitutional because it interferes with Congress’s exclusive power to regulate interstate commerce under Article I Section 8 of the Constitution. He further argued that if states were allowed to impose taxes like these, they would be able to interfere with congressional authority in ways never intended by our Founding Fathers when they wrote our nation's constitution. Furthermore, he noted that allowing states to levy taxes on goods crossing their borders could lead them into economic warfare against each other which would ultimately hurt consumers across all states due its destabilizing effects on prices and markets for those goods involved in interstate trade or transportation