Ketchum v. St. Louis is a United States Supreme Court case that was decided in 1879. The case involved a dispute between the City of St. Louis and the St. Louis and Iron Mountain Railroad Company. The City of St. Louis had granted the railroad company a right-of-way through the city, but the city later attempted to revoke the right-of-way. The railroad company argued that the city had no authority to revoke the right-of-way, as it had been granted by the state legislature. The Supreme Court agreed with the railroad company, ruling that the city had no authority to revoke the right-of-way. The Court held that the right-of-way was a contract between the railroad company and the state legislature, and that the city had no authority to interfere with the contract. The Court also held that the city had no authority to impose additional conditions on the right-of-way, as the state legislature had already granted the right-of-way. The Court's decision in Ketchum v. St. Louis established the principle that the state legislature has the authority to grant rights-of-way, and that the city cannot interfere with those rights-of-way. The decision also established that the city cannot impose additional conditions on rights-of-way that have already been granted by the state legislature.

Justice Field delivered the dissenting opinion in Ketchum v. St. Louis, arguing that the city of St. Louis had not acted unlawfully when it issued bonds to finance a railroad project and then sold them at a discount rate to raise funds for its own use. He argued that while there may have been some irregularity in how the bonds were handled, this did not amount to an illegal act as defined by law or precedent; rather, he maintained that such transactions are common practice among municipalities and should be allowed without legal repercussions so long as they do not violate any laws or regulations set forth by Congress or state legislatures. Furthermore, Justice Field noted that even if there was some illegality involved with issuing these discounted bonds, it would only affect those who purchased them from St. Louis after being aware of their discounted status - which was not applicable in this case since Ketchum had bought his bond before knowing about its reduced value - thus making him ineligible for damages under existing law due to lack of harm caused directly by the city's actions