The Maxwell Land-Grant Case was a United States Supreme Court case that dealt with the issue of whether the United States government had the right to take land from a private citizen without providing just compensation. The case was brought by the heirs of a man named Maxwell, who had been granted a large tract of land in New Mexico by the Mexican government in 1841. The United States had acquired the land from Mexico in 1848, and the Maxwell heirs argued that the United States had taken their land without providing just compensation. The Supreme Court ruled in favor of the Maxwell heirs, holding that the United States had indeed taken the land without providing just compensation. The Court held that the Fifth Amendment of the United States Constitution, which states that private property shall not be taken for public use without just compensation, applied to the Maxwell heirs. The Court also held that the United States had not provided just compensation for the land, and that the Maxwell heirs were entitled to receive compensation for the land taken by the United States. The Maxwell Land-Grant Case was an important case in the development of the law of eminent domain in the United States. The case established that the Fifth Amendment of the United States Constitution applies to the taking of private property by the government, and that the government must provide just compensation for any land taken. The case also established that the government must provide just compensation for any land taken, regardless of whether the land was acquired from a foreign government or from a private citizen.

In the Maxwell Land-Grant Case, the Supreme Court was asked to determine whether a grant of land by Congress in 1866 could be used as collateral for a loan. The majority opinion held that it could not because such an act would violate the Constitution's prohibition against impairing contracts. Justice Field dissented from this decision and argued that Congress had acted within its authority when it granted the land in question and therefore should have been allowed to use it as collateral for a loan. He further argued that if Congress had intended to limit its power over public lands, they would have done so explicitly in their legislation rather than leaving it open to interpretation by courts. Finally, he noted that while there may be some constitutional limits on Congressional powers with respect to public lands, those limits were not applicable here since no contract between private parties was impaired or affected by allowing this particular transaction involving government property.