John Quincy Adams (1767–1848), the sixth U.S. president (1825–1829) and eldest son of John Adams, was a brilliant diplomat who served as Secretary of State, where he negotiated the Adams–Onís Treaty (1819) to acquire Spanish Florida and helped craft the Monroe Doctrine. After a bitterly contested 1824 election decided by the House of Representatives—which critics dubbed a "corrupt bargain" with Henry Clay—his ambitious agenda for infrastructure and a national university was blocked by Congress, leading to a decisive defeat by Andrew Jackson in 1828. In a unique political comeback, he returned to Congress as a U.S. Representative from Massachusetts in 1830, becoming the only former president to serve in the House. There, he became a fierce opponent of slavery, leading the fight to repeal the "gag rule" that suppressed anti-slavery petitions and, at age 73, successfully defending the enslaved mutineers of the Amistad before the Supreme Court in 1841. He died of a stroke on the House floor in 1848, leaving a legacy as a tireless advocate for free speech and human rights.