The Philadelphia and Wilmington Railroad Company (PWR) brought a case against the State of Maryland to the Supreme Court. PWR argued that Maryland's tax on out-of-state railroads was unconstitutional, as it violated the Commerce Clause of the United States Constitution. The court ruled in favor of PWR, finding that while states have some power to regulate interstate commerce, they cannot impose taxes or duties which discriminate against citizens from other states. This ruling established an important precedent for future cases involving state taxation and interstate commerce. It also set forth a clear limitation on how far states can go when attempting to regulate activities across their borders without violating constitutional rights.

In the dissenting opinion of The Philadelphia and Wilmington Railroad Company v. The State of Maryland, Chief Justice Taney argued that the state had no authority to tax a federal corporation such as this railroad company. He reasoned that since Congress was given exclusive power over interstate commerce by the Constitution, any attempt by a state to regulate or interfere with it would be unconstitutional. Furthermore, he noted that if states were allowed to impose taxes on these corporations then they could effectively control their operations which would ultimately lead to an unequal distribution of commercial benefits among different states in violation of Article IV Section 2 Clause 1 (the Privileges and Immunities Clause). In conclusion, Chief Justice Taney believed that allowing Maryland's tax on this railroad company violated both constitutional principles and should not have been upheld by the Court.