In St. Louis, Iron Mountain & Southern Railway Company v. Southern Express Company, the Supreme Court of the United States was asked to decide whether a railroad company could be held liable for damages caused by a third-party express company. The express company had been hired by the railroad to transport goods, and the goods were damaged in transit. The railroad argued that it was not liable for the damages because it had not been directly responsible for the damage. The Supreme Court held that the railroad was liable for the damages caused by the express company. The Court reasoned that the railroad had a duty to exercise reasonable care in selecting a competent express company, and that it had failed to do so. The Court also held that the railroad was liable for the damages because it had assumed control over the goods and had a duty to protect them. The Court's decision established that a railroad company can be held liable for damages caused by a third-party express company if the railroad company fails to exercise reasonable care in selecting a competent express company and fails to protect the goods in its control.

In St. Louis, Iron Mountain & Southern Railway Company v. Southern Express Company, the Supreme Court was tasked with determining whether a railroad company could be held liable for damages caused by an express company’s negligence in failing to properly secure its freight cars on the railroad's tracks. The majority opinion found that the railway company had no liability because it did not have control over how the express company secured its freight cars and thus could not be responsible for any resulting damage or injury from their negligence. Justice Field dissented from this decision, arguing that under common law principles of agency and respondeat superior (the legal doctrine which holds employers vicariously liable for torts committed by employees), if there is evidence of actual control exercised by one party over another then they can be held accountable even if they are not directly at fault. He argued that since there was sufficient evidence to show that the railway had some degree of control over how goods were loaded onto trains operated on their lines, then they should bear responsibility when those goods cause harm due to improper loading or securing methods used by other companies operating on their rails.