Keystone Manganese and Iron Company v. Martin was a Supreme Court case that was decided in 1924. The case involved a dispute between Keystone Manganese and Iron Company and Martin, a former employee of the company. Martin had been employed by the company for several years and had been promised a bonus if he stayed with the company for a certain period of time. When the time came for the bonus to be paid, the company refused to pay it, claiming that Martin had not fulfilled his duties as an employee. Martin then sued the company for breach of contract, and the case eventually made its way to the Supreme Court. The Court held that the company had indeed breached its contract with Martin, and that he was entitled to the bonus he had been promised. The Court also held that the company was liable for damages, and ordered it to pay Martin the bonus plus interest. The decision in this case was important because it established that employers must honor their contractual obligations to their employees. It also established that employees can sue their employers for breach of contract if they fail to fulfill their obligations. This case is still cited today as an example of the importance of honoring contractual obligations.

In the dissenting opinion of Keystone Manganese and Iron Company v. Martin, Justice Holmes argued that the majority's decision was too broad in its interpretation of a contract between two parties. He believed that it should be up to each individual case to determine whether or not an agreement had been made, rather than relying on general principles as the majority did. Furthermore, he felt that there were certain circumstances where one party could reasonably expect another to act in accordance with their verbal agreement even if no written document existed. In this particular case, Justice Holmes found evidence suggesting that both parties intended for a contract to exist despite its lack of formalization; thus he would have ruled in favor of Martin instead of Keystone Manganese and Iron Company.