The Railroad Company v. Maryland is a United States Supreme Court case that was decided in 1873. The case involved a dispute between the state of Maryland and the Baltimore and Ohio Railroad Company. The state of Maryland had imposed a tax on the railroad company, which the company argued was unconstitutional. The Supreme Court ultimately ruled in favor of the railroad company, finding that the tax was unconstitutional because it violated the Commerce Clause of the United States Constitution. The Supreme Court held that the tax imposed by the state of Maryland was unconstitutional because it interfered with interstate commerce. The Court reasoned that the tax was discriminatory in nature, as it only applied to the railroad company and not to other businesses. Furthermore, the Court found that the tax was an undue burden on interstate commerce, as it would have a negative effect on the railroad company's ability to compete with other businesses. The Court's decision in this case was significant because it established the principle that states cannot impose taxes that interfere with interstate commerce. This decision has been cited in numerous subsequent cases involving the Commerce Clause, and it has been used to protect businesses from discriminatory taxes.

Justice Field delivered the dissenting opinion in The Railroad Company v. Maryland, arguing that the state of Maryland had no authority to tax a federal corporation such as the Baltimore and Ohio Railroad Company (B&O). He argued that since B&O was created by an act of Congress, it was subject only to federal laws and regulations. Furthermore, he noted that if states were allowed to impose taxes on corporations chartered by Congress, then they would be able to interfere with interstate commerce which is prohibited under Article I Section 8 of the Constitution. Field also pointed out that while some states may have imposed similar taxes on other types of businesses or individuals within their borders without violating any constitutional provisions, this did not mean those same actions could be taken against federally chartered corporations like B&O. In conclusion, Justice Field concluded that allowing states to tax these entities would lead to a “conflict between State legislation and Federal legislation” which should never occur in our system of government.