Hannewinkle v. Georgetown was a case heard by the United States Supreme Court in 1872. The case involved a dispute between two parties over a contract for the sale of a piece of land in the District of Columbia. The plaintiff, Hannewinkle, had entered into a contract with the defendant, Georgetown, to purchase a piece of land for $2,000. However, Georgetown refused to convey the land to Hannewinkle, claiming that the contract was invalid because it had not been properly executed. Hannewinkle argued that the contract was valid and that Georgetown was obligated to convey the land to him. The Supreme Court agreed with Hannewinkle, ruling that the contract was valid and that Georgetown was obligated to convey the land to him. The Court held that the contract was binding and enforceable, and that Georgetown was liable for damages for its breach of the contract. The Court's decision in Hannewinkle v. Georgetown established the principle that a contract is binding and enforceable even if it has not been properly executed. This decision has been cited in numerous subsequent cases involving contract disputes.

In Hannewinkle v. Georgetown, the Supreme Court was asked to determine whether a contract between two parties could be enforced when it had been made in violation of an existing law. The majority opinion held that such contracts were not enforceable, but Justice Field dissented from this decision. He argued that while laws should generally be respected and followed, there are certain cases where enforcing a contract would serve justice better than disregarding it entirely. In particular, he noted that if the parties involved had acted in good faith and without knowledge of any legal impediment to their agreement then they should not suffer for their ignorance or lack of awareness about the applicable law. Furthermore, he reasoned that allowing courts to refuse enforcement on these grounds might lead to unfairness as one party may have already performed its obligations under the agreement before learning of its illegality and thus would receive no compensation for doing so despite having acted in good faith throughout the process.