Spencer v. Merchant was a United States Supreme Court case that addressed the issue of whether a state court could enforce a contract that was made in another state. The case involved a contract between two parties, Spencer and Merchant, in which Spencer agreed to pay Merchant a certain amount of money for the sale of a piece of property. Merchant sued Spencer in a state court in New York for breach of contract. Spencer argued that the contract was made in Pennsylvania and that the New York court had no jurisdiction to enforce it. The Supreme Court held that the New York court did have jurisdiction to enforce the contract. The Court reasoned that the contract was valid and enforceable in the state where it was made, and that the New York court could enforce it as long as it did not conflict with the laws of the state where the contract was made. The Court also held that the New York court could not impose any additional requirements or conditions on the contract that were not part of the original agreement. The decision in Spencer v. Merchant established that a state court can enforce a contract that was made in another state, as long as it does not conflict with the laws of the state where the contract was made. This decision has been cited in numerous subsequent cases and has become an important part of contract law in the United States.

In Spencer v. Merchant, the Supreme Court was asked to decide whether a state court had jurisdiction over an action brought by a citizen of one state against another in which the amount in controversy exceeded $500. The majority opinion held that it did not have such jurisdiction and reversed the judgment of the lower court. Justice Field dissented from this decision, arguing that Congress had granted states broad powers to determine their own jurisdictional rules and that these should be respected unless they were clearly unconstitutional or otherwise prohibited by federal law. He further argued that there was no evidence here of any violation of constitutional rights or other prohibition on state authority, so he would have affirmed the ruling below granting jurisdiction to the state court.