James K. Polk

James Knox Polk (; November 2, 1795 – June 15, 1849) was the 11th president of the United States, serving from 1845 to 1849. A protégé of Andrew Jackson and a member of the Democratic Party, he was an advocate of American expansionism and Jacksonian democracy. Polk saw Texas join the Union in his first year in office; the annexation of the formerly independent republic, which had declared independence from Mexico, was one of the precipitating causes that soon led the U.S. into the Mexican–American War. The settlement of that war expanded American territory to the Pacific Ocean. During his term, the dispute with the United Kingdom over the Oregon Territory was resolved as well, creating the present U.S.-Canadian border.

After building a successful law practice in Tennessee, Polk was elected to its state legislature in 1823 and then to the United States House of Representatives in 1825, becoming a strong supporter of Jackson. Following his tenure as chairman of the Ways and Means Committee, he became Speaker of the House in 1835, the only person to serve both as Speaker and U.S. president. Polk left Congress to run for governor of Tennessee, winning in 1839 but losing in 1841 and 1843. He was a dark-horse candidate in the 1844 presidential election as the Democratic Party nominee. Polk entered his party's convention as a potential nominee for vice president but emerged as a compromise to head the ticket when no presidential candidate could gain the necessary two-thirds majority. In the general election, he narrowly defeated Henry Clay of the Whig Party and pledged to serve only one term.

After a negotiation fraught with the risk of war, Polk reached a settlement with Great Britain over the disputed Oregon Country, with the territory for the most part divided along the 49th parallel. He oversaw U.S. victory in the Mexican–American War, resulting in Mexico's cession of the entirety of the American Southwest. He secured a substantial reduction of American tariff rates with the Walker tariff of 1846. The same year, he achieved his other major goal, the reestablishment of the Independent Treasury system. True to his campaign pledge to serve one term (one of the few U.S. presidents to make and keep such a pledge), Polk left office in 1849 and returned to Tennessee, where he died of cholera soon afterward.

Though he has become relatively obscure, scholars have ranked Polk in the upper tier of U.S. presidents, largely for his ability to promote and achieve the major items on his presidential agenda. At the same time, he has been criticized for leading the country into a war with Mexico that exacerbated sectional divides. A property owner who used slave labor, he kept a plantation in Mississippi and increased his slave ownership during his presidency. Polk's policy of territorial expansion saw the nation reach the Pacific coast and almost all its contiguous borders. He helped make the U.S. a nation poised to become a great power, but his policies gravely exacerbated divisions between the free and slave states, setting the stage for the American Civil War.