Armstrong v. Morrill was a United States Supreme Court case that was decided in 1871. The case involved a dispute between two parties over a contract for the sale of a steamboat. The plaintiff, Armstrong, had contracted with the defendant, Morrill, to purchase a steamboat for $2,000. Armstrong paid the full amount, but Morrill refused to deliver the boat. Armstrong then sued Morrill for breach of contract. The Supreme Court held that the contract was valid and enforceable. The Court found that the contract was supported by consideration, meaning that both parties had given something of value in exchange for the other's promise. The Court also found that the contract was not voidable due to any fraud or misrepresentation on the part of Morrill. The Court held that Armstrong was entitled to damages for the breach of contract. The Court ordered Morrill to pay Armstrong the full purchase price of the steamboat, plus interest, and to pay for any additional costs incurred by Armstrong in bringing the suit. The Court also ordered Morrill to pay Armstrong's attorney's fees. In conclusion, the Supreme Court held that Armstrong was entitled to damages for the breach of contract and ordered Morrill to pay the full purchase price of the steamboat, plus interest, and to pay for any additional costs incurred by Armstrong in bringing the suit. The Court also ordered Morrill to pay Armstrong's attorney's fees.

In Armstrong v. Morrill, the Supreme Court was asked to decide whether a state law that allowed for an increase in taxes on certain property owners was constitutional. The majority opinion held that it was not unconstitutional because the tax did not violate any of the protections provided by either federal or state constitutions. However, Justice Field dissented from this decision and argued that while states have broad powers when it comes to taxation, they must still adhere to fundamental principles of fairness and equality when enacting such laws. He noted that this particular law unfairly targeted only those who owned land within a specific area and thus violated their right to equal protection under the law as guaranteed by both federal and state constitutions. Furthermore, he argued that if states are allowed to pass laws which target individuals based solely on where they live then there is no limit on what other types of discriminatory legislation could be passed in future cases.