Tyler was raised with his two brothers and five sisters on Greenway Plantation, a 1,200-acre estate with a six-room mansion. The crops including wheat, corn, and tobacco were tended to by the Tylers' forty slaves.
Tyler served three terms in Congress from 1816 to 1821. The dominant issue of the Sixteenth Congress (1819–21) was the admission of Missouri to the Union, and whether slavery would be permitted in the new state. Tyler was a leader in opposition to the Missouri Compromise of 1820 (which would for the first time establish national boundaries for the institution of slavery.) Tyler argued that the compromise served only to diminish and divide the states. He argued that if slavery was allowed in Missouri, it would attract existing slaveowners from Southern states, and in turn dilute the population of slaves, reducing each state's reliance on the practice. (By this time the importation of further slaves was illegal.) In his view, emancipation would occur at the state level through attrition, without federal intervention. Tyler voted against the Missouri Compromise (which passed) and all other bills to would restrict slavery in new territories.
From October 1829 to January 1830, Tyler served as a member of the Virginia state constitutional convention. The original Virginia Constitution gave outsize influence to the state's more conservative eastern counties, as it allocated an equal number of legislators to each county (regardless of population) and only gave the vote to property owners. The new convention gave the more populous and liberal counties of western Virginia an opportunity to expand their influence. As a slaveowner from eastern Virginia, Tyler supported the existing system and was opposed to any changes. But he was not an active participant during the debate, because he did not wish to alienate any of the state's political factions.
Tyler, an advocate of Western expansionism, made the annexation of the Republic of Texas part of his platform soon after becoming President. He intended annexation to be the focal point of his administration. Secretary Webster, opposed, convinced Tyler to focus on Pacific initiatives until later in his term. Tyler appointed Abel P. Upshur as his new Secretary of State, and Tyler and Upshur began quiet negotiations with the Texas government, promising military protection from Mexico in exchange for a commitment to annexation. Upshur planted rumors of possible British designs on Texas to drum up support among Northern voters, who were wary of admitting a new pro-slavery state. Tyler appointed former Vice President John C. Calhoun in early March 1844 as his Secretary of State, following the death of Upshur. Calhoun was a leading advocate of slavery, and his attempts to get an annexation treaty passed were resisted by abolitionists. Martin Van Buren also worked, behind the scenes of American politics, to ensure the annexation treaty was not approved. Even with the support of Andrew Jackson for the treaty, the United States Senate rejected it, 16–35. Tyler wanted the issue of the annexation of Texas to be the foundation of his re-election campaign. After the annexation treaty had been rejected, Tyler called for Congress to annex Texas by joint resolution rather than by treaty. When fellow expansionist James K. Polk had won the election, Tyler announced in his annual message to Congress that "a controlling majority of the people and a large majority of the states have declared in favor of immediate annexation." In late February 1845, the House by a substantial margin and the Senate by a bare 27–25 majority approved a joint resolution offering terms of annexation to Texas. On March 1, three days before the end of his term, Tyler signed the bill into law.
Tyler retired to a Virginia plantation, originally named "Walnut Grove" (or "the Grove"), located on the James River in Charles City County, Virginia. He renamed it "Sherwood Forest" to signify that he had been "outlawed" by the Whig Party. His neighbors, largely Whigs, appointed him "overseer" of his road in 1847 in an effort to mock him. To their displeasure he treated the title seriously, frequently summoning his neighbors' slaves to attend to road work, and continued to bear the title even after his neighbors asked him to stop.
Tyler was a slaveholder for his entire life. John Dunjee claimed to be the illegitimate son of John Tyler, a child of Tyler and one of his female slaves. Early in his presidency, Tyler was attacked by a newspaper alleging he had fathered (and sold) several sons with his slaves, prompting a strong denial from the Tyler administration linked newspaper the Madisonian. The allegation has never been proven to be true, but it likely grew legs because of Tyler's propensity to procreate. He holds the record for most children by a President: fifteen.