St. Germain v. Brunswick is a Supreme Court case from 1883. The case involved a dispute between two parties over a contract for the sale of a steamboat. The plaintiff, St. Germain, was the owner of the steamboat, and the defendant, Brunswick, was the buyer. The dispute arose when St. Germain refused to deliver the steamboat to Brunswick, claiming that the contract was void because it had been made without consideration. Brunswick argued that the contract was valid and that St. Germain was obligated to deliver the steamboat. The Supreme Court ruled in favor of Brunswick, finding that the contract was valid and that St. Germain was obligated to deliver the steamboat. The Court held that consideration was not necessary for a contract to be valid, and that the parties had agreed to the terms of the contract in good faith. The Court also held that St. Germain was not entitled to any damages for breach of contract, as Brunswick had not actually breached the contract. This case established the principle that consideration is not necessary for a contract to be valid, and that parties can enter into a contract in good faith without consideration. This principle has been applied in many subsequent cases, and is still used today.

In the dissenting opinion of St. Germain v. Brunswick, Justice Marshall argued that the majority's decision was wrong and should be reversed because it failed to consider a key point in this case: whether or not the state had jurisdiction over St. Germain’s property when he purchased it from his father-in-law in 1783. According to Justice Marshall, since there is no evidence that Maine had any authority over this land prior to its separation from Massachusetts in 1820, then St. Germain must have acquired title by virtue of his purchase before Maine became an independent state and thus has a valid claim on the property regardless of what happened afterwards with regards to boundary disputes between New Hampshire and Massachusetts (which later became Maine). He further argued that if such claims were allowed under these circumstances then other individuals who made similar purchases would also be able to make valid claims against their respective states as well which could lead to chaos within our legal system due to conflicting laws between different states regarding ownership rights for land previously owned by private citizens prior to their formation as separate entities