Gay's Gold was a landmark Supreme Court case that established the principle of equitable estoppel in the United States. The case involved a dispute between two parties over a gold mine in California. The plaintiff, Gay, had purchased the mine from the defendant, Smith, who had previously purchased it from a third party. Smith had failed to disclose to Gay that he had not obtained a valid title to the mine. Gay subsequently discovered that the title was invalid and sued Smith for damages. The Supreme Court held that Smith was estopped from denying Gay's title to the mine. Estoppel is a legal doctrine that prevents a party from denying or asserting something that is contrary to what they have previously said or done. In this case, Smith had previously represented to Gay that he had a valid title to the mine, and thus was estopped from denying it. The Court held that Smith was liable for damages to Gay for his misrepresentation. The decision in Gay's Gold established the principle of equitable estoppel in the United States, which has since been applied in numerous cases. The Court's decision was also significant in that it recognized the importance of good faith and fair dealing in contractual relationships. The Court held that parties to a contract must act in good faith and not misrepresent facts in order to protect the interests of the other party.

In Gay's Gold, the Supreme Court was asked to decide whether a contract between two parties that had been partially performed could be enforced. The majority opinion held that it could not because of the doctrine of partial performance, which states that contracts cannot be enforced if they have only been partially performed. However, in his dissenting opinion Justice Field argued that this case should be decided on its own merits and not by relying on an established legal principle. He noted that both parties had acted in good faith and were entitled to expect their agreement would be honored. Furthermore, he pointed out there was no evidence either party intended to defraud or deceive each other; thus enforcing the contract would serve justice better than allowing one side to benefit from another’s mistake or misfortune. In conclusion, Justice Field believed the court should uphold the contract as valid since it met all requirements for enforceability under existing law and did not violate any public policy considerations