The Amistad, known formally as United States v. The Libellants and Claimants of the Schooner Amistad, her Tackle, Apparel and Furniture, together with her Cargo, and the Africans mentioned in the Several Libels and Claims, was one of the most significant cases involving slavery to come before the Supreme Court.

On 28 June 1839, the schooner Amistad left Havana for Puerto Principe, a Cuban coastal town. Its crew consisted of five whites, a mulatto cook, and a black cabin boy along with a cargo of wine, gold, silk, saddles, and fifty-three slaves, forty-nine adults and four children. The slaves had been recently imported from Africa in violation of Spanish law. On the fourth night at sea, the slaves freed themselves and mutinied, killing the captain and the mulatto cook. Two of the crew escaped overboard. The two owners of the slaves, Jose Ruiz and Pedro Montes, both citizens of Spain, barely escaped being murdered, apparently because the African mutineers realized that they needed them in order to sail the ship. Over the next six weeks the slaves commanded Montes to sail back to their homeland, present-day Sierra Leone. Instead, Montes guided the ship on a zig-zag course to the eastern shore of Long Island. There, on 26 August 1839, the ship and its cargo were discovered, first by two sea captains shooting birds, and then by the U.S. Coast Guard brig Washington. Both the sea captains and the crew of the Washington laid claim to the cargo under the law of salvage. The Washington seized the Amistad and its cargo, including the slaves, and took them to New London, Connecticut.

Over the next two years the slaves and their ostensible owners became engulfed in a major cause celebre that energized the fledgling anti-slavery movement and intensified the conflict over slavery. A small but energetic group of abolitionists, headed by Lewis Tappan, organized the “Amistad Committee” to seek funds and legal support for the captured Africans. The administration of President Martin Van Buren, on the other hand, insisted that the slaves and the cargo should be turned over to their Spanish owners under the provisions of a treaty with Spain of 1795. That agreement provided that property of one country taken possession of in the territorial waters of another country had to be returned to their owners. The Van Buren administration urged the federal court in Connecticut to comply with the request of the Spanish government that the “slaves” be extradited to Spain to stand trial for murder and mutiny and that the cargo be returned to its owners. Failing that action, the United States wanted the Africans tried as criminals in the United States.

In the lower federal courts, Roger S. Baldwin, a future governor of Connecticut, argued on behalf of the Africans. Baldwin insisted that the alleged mutiny had occurred in international waters and therefore the United States had no jurisdiction to punish the Africans. Baldwin also argued that the United States should not act as a slave-catcher for foreign slave-holders, especially since Spanish law explicitly disavowed the African slave trade. Justice Smith Thompson, who presided over the case as part of his circuit-riding duties, found in favor of the Africans. Thompson, however, refused to decide the question of whether they were slaves and, as such, the property of Ruiz and Montes. Instead, he ordered a civil trial to determine their status.

The civil trial began in New Haven on 8 January 1840. President Van Buren, in anticipating the outcome, ordered a naval warship to stand by in the harbor to whisk the Africans back to Havana before they could file an appeal. The court, however, found for the Africans. Baldwin filled the courtroom with horrific stories of the Middle Passage and abuse of the Africans by the Spanish. District Judge Andrew T. Judson responded by finding that the Africans had been born free, that they were kidnapped from their homeland of Africa, and that they should be returned there. The Van Buren administration immediately appealed, but Justice Thompson, on circuit, upheld Judson's ruling, modifying it only to provide that the decision about returning to Africa was entirely the choice of the Africans. The United States government had no obligation to pay their way back home, a clearly gratuitous holding since the Africans were essentially destitute.

The Van Buren administration appealed again, this time to the Supreme Court. Such an appeal made sense, because five of the nine justices were southerners who either owned or had owned slaves. Van Buren also believed that maintaining strong relations with Spain depended on complying fully with the 1795 treaty.

Fearing the high court might overturn the victories won below, Tappan persuaded Congressman and former President John Quincy Adams, then 74, to join with Baldwin in arguing the case before the high court. Adams launched a blistering attack against the actions of President Van Buren and the entire notion that the chief executive had a duty to return slaves based on the 1795 treaty. Adams also ridiculed southern intellectuals for their defense of slavery, invoked the Bible in support of the proposition that public officials had a duty to provide for human freedom, and insisted that the Declaration of Independence, with its claim that all men are created equal, settled the matter of how to dispose of the Africans.

Justice Joseph Story wrote for the majority. (During the time between the oral arguments and the decision by the Court, Justice Phillip P. Barbour died.) Story leaned heavily on the narrow legal reasoning of Roger Baldwin rather than Adams's extraordinarily powerful yet bitterly sarcastic arguments. Story found that the Africans had been kidnapped; they were “property rescued from pirates” (p. 132). Given this reality, Story concluded that even under the laws of Spain the slaves were due their freedom. The United States government had no responsibility to return them either to the Spanish government or to Ruiz and Montes. Story insisted that the 1795 treaty, when it addressed the issue of returning “merchandize,” meant goods, not human beings. For slaves to be returned as property under international law, the treaty governing them had to specify explicitly that “property’ meant slaves. The 1795 treaty did not. According to Story, the condition of being property could not be implied to human beings. Story also affirmed Thompson's finding that the Africans were free to stay in or leave the United States, but the government had no obligation to pay for their travel back to Sierra Leone. Justice Henry Baldwin of Pennsylvania casted a lone, unwritten dissent.

The Amistad Committee eventually raised sufficient funds to pay for the return voyage of the Africans, who left in November 1841. Only one African, Sarah, ever returned to America. She attended Oberlin College. For the next two decades the Spanish government pressed the United States for compensation, but John Quincy Adams led the opposition against that effort until his death in 1847. With the election of President Abraham Lincoln in 1860, Spain's efforts ended and the debate over slavery passed from the courtroom to the battlefield.

— Kermit L. Hall