Hannibal Railroad v. Swift was a case heard by the United States Supreme Court in 1871. The case involved a dispute between the Hannibal Railroad Company and the Swift family over the ownership of a piece of land in Missouri. The Swift family had been granted the land by the United States government in 1837, but the Hannibal Railroad Company had been granted a right-of-way over the land in 1851. The Swift family argued that the right-of-way granted to the railroad company was invalid because it had been granted without their consent. The Supreme Court ultimately sided with the Hannibal Railroad Company, ruling that the right-of-way was valid and that the Swift family had no legal right to the land. The Court held that the right-of-way was a valid exercise of the power of eminent domain, and that the Swift family had no legal right to the land because they had not taken any steps to assert their ownership. The Court also held that the right-of-way was a valid exercise of the power of eminent domain because it was necessary for the public good. The decision in Hannibal Railroad v. Swift established the principle that the government has the power to take private property for public use, as long as it is done in a fair and reasonable manner. This principle has been applied in numerous cases since then, and is still an important part of the law today.

In the dissenting opinion of Hannibal Railroad v. Swift, Justice Field argued that the majority's decision was contrary to established precedent and would create an unfair burden on railroad companies. He noted that prior cases had held that a contract between two parties could not be altered without mutual consent, and thus it should have been up to both parties in this case - Hannibal Railroad and Swift - to agree upon any changes or modifications made to their original agreement. Furthermore, he argued that if one party were allowed unilaterally alter the terms of a contract after it had already been agreed upon by both sides, then no contracts would ever be safe from alteration or modification at any time during its duration. As such, Justice Field concluded his dissent by urging for greater protection for contracts against unilateral alterations so as to ensure fairness among all involved parties.