Wheeler v. Sage was a United States Supreme Court case that dealt with the issue of whether or not an individual could be held liable for damages caused by their negligence in failing to properly secure a horse and wagon. The plaintiff, Wheeler, had been injured when his carriage collided with the defendant's unsecured horse and wagon on a public road. In its decision, the court found that although there was no specific law requiring individuals to secure their horses and wagons while traveling on public roads, it was still necessary for them to do so as part of their duty of care towards others using those same roads. As such, they were liable for any damage caused by failure to exercise this duty of care. Ultimately, the court ruled in favor of Wheeler and awarded him damages from Sage due to his negligence in securing his horse and wagon before taking it out onto public roads.

In Wheeler v. Sage, the Supreme Court was asked to decide whether a contract between two parties could be enforced when it had been made in violation of an existing state law. The majority opinion held that the contract was void and unenforceable due to its illegality under state law. However, Justice Grier dissented from this decision on the grounds that enforcing contracts is essential for commerce and economic stability, so courts should not invalidate them lightly or without clear evidence of their unlawfulness. He argued that since there were no allegations of fraud or misrepresentation by either party in this case, nor any proof that they knew about the relevant statute at issue before entering into their agreement, then it would be unjust to deny enforcement simply because one party later discovered a technical violation of some obscure provision in a local ordinance which neither side had ever heard about before.