Mustin v. Cadwalader was a United States Supreme Court case that dealt with the issue of whether a party could be held liable for a breach of contract when the contract was not in writing. The case involved a dispute between two parties, Mustin and Cadwalader, over a contract for the sale of a steamboat. Mustin claimed that he had an oral agreement with Cadwalader to purchase the steamboat, while Cadwalader argued that no such agreement existed. The Supreme Court held that Mustin could not be held liable for a breach of contract because the contract was not in writing. The Court reasoned that, under the Statute of Frauds, contracts for the sale of goods must be in writing in order to be enforceable. The Court also noted that, even if the parties had an oral agreement, it would not be enforceable because it was not in writing. The Court's decision in Mustin v. Cadwalader established that, in order for a contract to be enforceable, it must be in writing. This decision has been cited in numerous subsequent cases and is still used today to determine whether a contract is enforceable.

In Mustin v. Cadwalader, the Supreme Court was tasked with determining whether a contract between two parties that had been partially performed could be enforced in court. The majority opinion found that it could not, as the statute of frauds required all contracts to be in writing and signed by both parties for them to be enforceable. Justice Field dissented from this opinion, arguing that partial performance should suffice when there is no dispute about what has already been done or agreed upon between the two parties involved. He argued further that if courts were allowed to consider evidence of partial performance then many cases would have a better chance at being resolved without resorting to costly litigation over matters which are otherwise clear-cut and undisputed.