United States v. Iron Silver Mining Company was a Supreme Court case that was decided in 1891. The case involved a dispute between the United States and the Iron Silver Mining Company over the ownership of certain mining claims in Colorado. The United States argued that the mining claims were part of the public domain and that the Iron Silver Mining Company had no right to them. The Iron Silver Mining Company argued that they had acquired the claims through a valid mining location and that they had a right to them. The Supreme Court ultimately sided with the United States, ruling that the Iron Silver Mining Company had no right to the mining claims. The Court held that the mining claims were part of the public domain and that the Iron Silver Mining Company had not acquired them through a valid mining location. The Court also held that the United States had the right to reclaim the mining claims and that the Iron Silver Mining Company had no right to them. This decision established the principle that the United States has the right to reclaim public lands that have been improperly claimed by private individuals or companies.

In the dissenting opinion of United States v. Iron Silver Mining Company, Justice Field argued that the majority’s decision was wrongfully based on a misreading of the relevant statute and failed to consider Congress’ intent in passing it. He noted that when Congress passed this law, they intended for it to be applied only to those who had already acquired rights from the government prior to its passage; however, he believed that by ruling as they did, the majority had effectively extended these rights retroactively which would have been an unconstitutional act. Furthermore, he argued that since there was no evidence presented at trial indicating any such pre-existing right held by Iron Silver Mining Company or their predecessors in title before 1866 (the year in which this law was enacted), then there could not possibly have been any liability under this statute for them and thus their conviction should be reversed.