Clark v. United States was a case heard by the United States Supreme Court in 1881. The case involved a dispute between the United States and the heirs of a deceased man, John Clark, over the ownership of a tract of land in the state of Arkansas. The United States had acquired the land from the Choctaw Nation in 1820, and had subsequently sold it to Clark in 1836. Clark had died in 1845, and his heirs had continued to occupy the land until 1876, when the United States brought suit to recover the land. The Supreme Court held that the United States had a valid claim to the land, as the Choctaw Nation had not had the authority to sell the land to Clark in the first place. The Court noted that the Choctaw Nation had been a dependent nation, and that the United States had the exclusive right to acquire land from them. The Court also held that the United States had not waived its right to the land by allowing Clark and his heirs to occupy it for so long, as the United States had not been aware of the occupation until 1876. The Court thus held that the United States had a valid claim to the land, and that the heirs of John Clark had no right to the land. The Court ordered the heirs to vacate the land and to pay the United States for the improvements they had made to the land.

In Clark v. United States, the Supreme Court was asked to decide whether a defendant could be convicted of an offense that was not specifically mentioned in the indictment against them. The majority opinion held that such convictions were permissible as long as they arose out of the same transaction or set of facts alleged in the indictment and did not increase punishment beyond what had been prescribed by law for those offenses. Justice Field dissented from this decision, arguing that allowing defendants to be convicted on charges which had never been presented to them violated their right to due process under both common law and constitutional principles. He argued further that it undermined public confidence in judicial proceedings by creating uncertainty about what crimes a person might actually be charged with after being indicted for one particular crime.