McElrath 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 a private citizen, William McElrath, over the ownership of a parcel of land in the state of Arkansas. McElrath had purchased the land from the United States in 1871, but the United States later claimed that the land had been improperly sold and sought to reclaim it. The Supreme Court held that the United States had not established its right to the land, and that McElrath was the rightful owner. The Court reasoned that the United States had failed to prove that the land had been improperly sold, and that McElrath had acted in good faith when he purchased the land. The Court also noted that the United States had failed to provide any evidence that the land had been improperly sold. The Court's decision in McElrath v. United States established that the United States must prove its right to reclaim land that it has sold to a private citizen. The decision also established that the United States must provide evidence to support its claim that the land was improperly sold. The decision has been cited in numerous subsequent cases involving disputes between the United States and private citizens over the ownership of land.

In the case of McElrath v. United States, the Supreme Court was asked to decide whether a federal statute that allowed for an individual's property to be seized and sold in order to pay off debts owed by them was constitutional. The majority opinion held that it was constitutional, but Justice Field dissented from this decision. He argued that Congress had no authority under the Constitution to pass such a law as it violated both due process and equal protection clauses of the Fifth Amendment. Furthermore, he argued that allowing individuals' property to be taken without any form of judicial review or hearing would lead to arbitrary seizures with no way for those affected by them to challenge their legality or obtain compensation if they were wrongfully taken away from them. In conclusion, Justice Field believed that Congress did not have the power under the Constitution nor should it have been given such power over private citizens’ rights and liberties without proper safeguards in place against potential abuse or misuse of its authority