Cook v. Lillo is a United States Supreme Court case that was decided in 1881. The case involved a dispute between two parties over a contract for the sale of a steamboat. The plaintiff, Cook, was the owner of the steamboat and the defendant, Lillo, was the buyer. Cook had agreed to sell the steamboat to Lillo for a certain price, but Lillo failed to make the payments as agreed. Cook then sued Lillo for breach of contract. The Supreme Court held that the contract between the parties was valid and enforceable. The Court found that the contract was supported by consideration, meaning that each party had given something of value in exchange for the other's promise. The Court also found that the contract was not void for lack of mutuality, meaning that both parties had an obligation to perform under the contract. The Court ultimately held that Lillo was liable for breach of contract and ordered him to pay the amount due to Cook. The Court also held that Cook was entitled to damages for the breach of contract, including the cost of repairs to the steamboat. This case established the principle that a contract is binding and enforceable when it is supported by consideration and mutuality.

In the case of Cook v. Lillo, Justice Field delivered a dissenting opinion in which he argued that the majority had erred in its interpretation of an 1845 Louisiana statute concerning succession rights to property. The majority held that when a person died intestate (without leaving a will), their children were entitled to inherit all of their estate, regardless if they had been born before or after the death of their parent. However, Justice Field disagreed with this ruling and instead believed that only those children who were born prior to the death should be allowed to succeed as heirs; any posthumous offspring would not have such rights under Louisiana law. He further noted that it was up to state legislatures - not courts -to decide how inheritance laws should be interpreted and applied within each jurisdiction's borders. Ultimately, his dissent was unsuccessful and did not sway the court's decision on this matter.