Like most contemporaries, John Quincy Adams' views on slavery evolved over time. Historian David F. Ericson asks why he never became an abolitionist. He never joined the movement called "abolitionist" by historians—the one led by William Lloyd Garrison—because it demanded the immediate abolition of slavery and insisted it was a sin to enslave people. Further, abolitionism meant disunion and Adams was a staunch champion of American nationalism and union.
He often dealt with slavery-related issues during his seventeen-year congressional career, which began after his presidency. In the House, Adams became a champion of free speech, demanding that petitions against slavery be heard despite a "gag rule" that said they could not be heard. Adams repeatedly spoke out against the "Slave Power", that is the organized political power of the slave owners who dominated all the southern states and their representation in Congress. He vehemently attacked the annexation of Texas (1845) and the Mexican War (1846–1848) as part of a "conspiracy" to extend slavery. During the censure debate, Adams said that he took delight in the fact that southerners would forever remember him as "the acutest, the astutest, the archest enemy of southern slavery that ever existed".
Biographers Nagle and Parsons argue that he was not a true abolitionist, although he quickly became the primary enemy of slavery in Congress. Though he, like most anti-slavery contemporaries such as Henry Clay, held the preservation of the union as the primary goal, he increasingly became more forceful for the anti-slavery cause. Remini notes that Adams feared that the end of slavery could only come through civil war or the consent of the slave South, and not quickly and painlessly as the abolitionists wanted.
Background
John Quincy Adams was born into a family that never owned slaves, and was hostile to the practice. His mother, Abigail Adams, held strong anti-slavery views. His father, President John Adams, despite opposing a 1777 bill in Massachusetts to emancipate slaves, opposed slavery on principle and considered the practice of slavery abhorrent. Adams' career before his election to presidency in 1824 was focused on foreign policy where the slavery issue seldom came up. There were no major slavery-related controversies during his presidency. The union issue became hotly contested under his successor, Andrew Jackson, when South Carolina threatened to secede, partly due to the tariff. This event, the Nullification Crisis, was successfully resolved, with a lower tariff and an end to threats of disunion.
The debate on the Missouri Compromise in 1820 was a turning point for Adams. During that debate, he broke with his friend John C. Calhoun, who became the most outspoken national leader in favor of slavery. They became bitter enemies. Adams vilified slavery as a bad policy while Calhoun countered that the right to own slaves had to be protected from interference from the federal government to keep the nation alive. Adams said slavery contradicted the principles of republicanism, while Calhoun said that slavery was essential to American democracy, for it made all white men equal. Adams predicted that if the South formed a new nation, it would be torn apart by an extremely violent slave insurrection. If the two nations went to war, Adams predicted the president of the United States would use his war powers to abolish slavery. The two men became ideological leaders of the North and the South.
Amistad case
In 1841, Adams had the case of a lifetime, representing the defendants in United States v. The Amistad Africans in the Supreme Court of the United States. He successfully argued that the Africans, who had seized control of a Spanish ship, La Amistad, on which they were being transported illegally as slaves, should not be extradited or deported to Cuba (a Spanish colony where slavery was legal) but should be considered free. Under President Martin Van Buren, the government argued the Africans should be deported for having mutinied and killed officers on the ship. Adams won their freedom, with the chance to stay in the United States or return to Africa. Adams made the argument because the U.S. had prohibited the international slave trade, although it allowed internal slavery. He never billed for his services in the Amistad case. The speech was directed not only at the justices of this Supreme Court hearing the case, but also to the broad national audience he instructed in the evils of slavery.