The U.S. Supreme Court case General American Tank Car Corp. v. El Dorado Terminal Co., 1939, revolved around a dispute over the interpretation of a contract between the two companies regarding tank car rentals and demurrage charges (penalties for exceeding agreed-upon time limits). The plaintiff, General American Tank Car Corporation, claimed that El Dorado Terminal Company had violated their agreement by failing to pay these charges in full. However, the defendant argued that they were not liable for such payments as per their understanding of the contract terms. The Supreme Court ruled in favor of General American Tank Car Corporation after interpreting ambiguous clauses within the contract against its drafter - which was El Dorado Terminal Company - following an established legal principle known as "contra proferentem". This rule holds that any ambiguity should be resolved against the party who imposed those conditions or drafted them into an agreement. This decision upheld lower court rulings and reinforced principles related to contractual interpretation under common law.

The dissenting opinion in the case of General American Tank Car Corp. v. El Dorado Terminal Co., argued that the majority's decision to hold General American liable for damages was incorrect, as it failed to consider certain key factors. The dissent emphasized that there were no explicit contractual obligations between General American and El Dorado regarding maintenance or inspection of tank cars, nor any statutory duty imposed by federal law on car owners to maintain their equipment while in lessees' possession. It also highlighted that the accident occurred due to a defect which could not have been discovered through ordinary inspections but required disassembly of parts - an action beyond routine maintenance expectations for leased equipment under common industry practice at the time. Therefore, according to this view, liability should rest with El Dorado who had control over and use of the tank car when damage occurred rather than its owner who had no knowledge or reasonable means of knowing about hidden defects.