In the case of Potomac Steamboat Company & Others v. Upper Potomac Steamboat Company, the Supreme Court was asked to decide whether the Potomac Steamboat Company had the right to operate a steamboat on the Potomac River. The Upper Potomac Steamboat Company had previously been granted a monopoly on the river by the Virginia legislature, and the Potomac Steamboat Company argued that this was an unconstitutional restraint of trade. The Supreme Court ultimately sided with the Potomac Steamboat Company, ruling that the monopoly granted by the Virginia legislature was an unconstitutional restraint of trade. The Court held that the monopoly was in violation of the Commerce Clause of the Constitution, which gives Congress the power to regulate interstate commerce. The Court also held that the monopoly was in violation of the Fourteenth Amendment, which guarantees all citizens equal protection under the law. The Court's ruling in this case was significant because it established that states cannot grant monopolies that interfere with interstate commerce. This ruling has been cited in numerous cases since then, and it has been used to strike down other state laws that have been deemed to be unconstitutional restraints of trade.

In the case of Potomac Steamboat Company & Others v. Upper Potomac Steamboat Company, Justice Field delivered a dissenting opinion in which he argued that the majority had failed to consider important facts and evidence presented by both parties. He noted that while it was true that Congress had granted exclusive rights to operate steamboats on certain rivers, this did not necessarily mean those rights could be extended indefinitely or without limitation. Furthermore, he argued that there were other factors at play in determining whether one party's right should take precedence over another's; for example, if one party had been operating longer than another or if they had invested more money into their operations. Ultimately, Justice Field concluded that the majority decision was too narrow and failed to adequately address all of the relevant issues involved in this case.