Simmons v. Wagner 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, Simmons and Wagner, in which Simmons agreed to pay Wagner a certain amount of money for a piece of land located in the state of Ohio. Wagner sued Simmons in the state of Ohio for breach of contract, and Simmons argued that the contract was not enforceable in Ohio because it had been made in the state of New York. The Supreme Court held that the contract was enforceable in Ohio, and that the state court had the authority to enforce it. The Court reasoned that the contract was valid and enforceable in Ohio because it had been made in a state that was a party to the Constitution, and that the contract was not in violation of any public policy of Ohio. The Court also noted that the contract was not in violation of any law of Ohio, and that the parties had the right to enter into the contract in the state of New York. The Court's decision in Simmons v. Wagner established that a state court could enforce a contract that was made in another state, provided that the contract was not in violation of any public policy or law of the state in which it was made. This decision has been cited in numerous cases since then, and it has been used to support the enforcement of contracts made in other states.

In Simmons v. Wagner, the Supreme Court was tasked with determining whether a contract between two parties could be enforced when one of the parties had died before it was fully executed. The majority opinion held that such contracts were not enforceable because they lacked consideration and mutuality of obligation. Justice Field dissented from this ruling, arguing that there should be an exception to this rule in cases where both parties have already performed their obligations prior to death or where performance is impossible due to death. He argued that if both sides had done what they promised then justice would require enforcement of the agreement even though it wasn't fully completed at the time of death. Furthermore, he noted that enforcing these agreements would encourage people to enter into them without fear of being unable to complete them due to unforeseen circumstances like death or illness. Ultimately, his dissent did not sway enough justices and so the majority opinion prevailed; however, his arguments remain relevant today as courts continue grapple with how best handle similar situations involving contracts and deaths