Hanna v. Maas 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, Maas and Hanna, in which Maas agreed to pay Hanna a certain amount of money for the sale of a piece of property. The contract was made in the state of New York, but Maas refused to pay the money and Hanna sued in the state of Illinois. The Supreme Court held that the state court in Illinois had the authority to enforce the contract, even though it was made in another state. The Court reasoned that the contract was valid and enforceable under the Full Faith and Credit Clause of the United States Constitution, which requires states to give full faith and credit to the public acts, records, and judicial proceedings of other states. The Court also noted that the contract was not contrary to the public policy of either state, and thus could be enforced. In conclusion, the Supreme Court held that the state court in Illinois had the authority to enforce the contract between Maas and Hanna, even though it was made in another state. The Court reasoned that the contract was valid and enforceable under the Full Faith and Credit Clause of the United States Constitution, and that it was not contrary to the public policy of either state.

In the case of Hanna v. Maas, the Supreme Court was tasked with determining whether a contract between two parties for the sale of land in Wisconsin could be enforced despite being made prior to Congress granting statehood to Wisconsin. The majority opinion held that since Congress had not yet granted statehood when the contract was formed, it lacked legal authority and thus could not be enforced. Justice Field dissented from this decision, arguing that although Congress had not yet granted statehood at the time of contracting, its subsequent action did grant retroactive validity to contracts entered into before then. He argued that such an interpretation would encourage settlers who were already living in territories awaiting admission as states by allowing them assurance their contracts would remain valid after admission occurred. Furthermore he noted that if these settlers knew their agreements might become invalid upon admission they may have been less likely or even unwilling to settle there in anticipation of becoming citizens of a new State