Deming's Appeal was a United States Supreme Court case that was decided in 1870. The case involved a dispute between two parties over a contract for the sale of land. The plaintiff, Deming, had entered into a contract with the defendant, Smith, to purchase a parcel of land. Smith had agreed to sell the land to Deming for a certain price, but then refused to complete the sale. Deming then sued Smith for breach of contract. The Supreme Court held that Smith was liable for breach of contract. The Court found that Smith had entered into a valid contract with Deming and that Smith had breached the contract by refusing to complete the sale. The Court also held that Deming was entitled to damages for the breach of contract. The Court awarded Deming the amount of money that he had paid to Smith as part of the contract, plus interest. The decision in Deming's Appeal established the principle that a party who breaches a contract is liable for damages. This principle has been applied in numerous cases since then and is still an important part of contract law today.

In Deming's Appeal, the Supreme Court was asked to decide whether a state court had jurisdiction over an action brought by a non-resident against another non-resident. The majority opinion held that it did not have such jurisdiction because the parties were both from different states and there was no connection between them or their dispute and the forum state. Justice Field dissented, arguing that under certain circumstances, a state court could exercise jurisdiction over cases involving out of state parties if they had sufficient contacts with the forum state. He argued that in this case, since one of the defendants resided in Connecticut for some time before moving away and still owned property there at the time of suit being filed, he should be considered as having sufficient contact with Connecticut to give its courts authority to hear his case.