Jennings v. Carson was a case heard by the United States Supreme Court in 1807. The dispute arose from a contract between Jennings and Carson, wherein Jennings agreed to build two vessels for Carson at an agreed upon price of $6,000 each. After completing one vessel, Jennings sued for payment but was denied on the grounds that he had not completed both ships as promised under the terms of their agreement. The Supreme Court ruled in favor of Jennings and held that since he had substantially performed his part of the bargain, he should be paid according to its terms regardless if it wasn't fully executed or not; this is known as substantial performance doctrine which allows parties who have fulfilled most (but not all) contractual obligations to receive compensation even if they did not fulfill every single term outlined in their agreement. This ruling established important precedent regarding contracts and has been cited numerous times throughout American legal history since then.

In Jennings v. Carson, the Supreme Court was tasked with determining whether a state court had jurisdiction to hear a case involving citizens of different states. The majority opinion held that it did not have such authority and dismissed the appeal. However, Justice Chase dissented from this decision and argued that the Constitution grants federal courts exclusive jurisdiction over cases between citizens of different states only when they involve diversity in citizenship as well as an amount in controversy exceeding $500; since neither condition applied here, he believed that state courts should be allowed to exercise their own discretion on matters within their respective jurisdictions. He further noted that if Congress had intended for all cases between citizens of different states to be heard exclusively by federal courts regardless of these conditions being met or not, then it would have been explicitly stated in the Judiciary Act or some other law passed by Congress rather than left up to judicial interpretation.