<P> James Knox Polk (November 2, 1795--June 15, 1849) was an American politician who served as the 11th President of the United States (1845--1849). He previously was Speaker of the House of Representatives (1835--1839) and Governor of Tennessee (1839--1841). A protégé of Andrew Jackson, he was a member of the Democratic Party and an advocate of Jacksonian democracy . During Polk's presidency, the United States expanded significantly with the annexation of the Republic of Texas, the Oregon Territory, and the Mexican Cession following the American victory in the Mexican--American War . </P> <P> After building a successful law practice in Tennessee, Polk was elected to the state legislature (1823) and then to the United States House of Representatives in 1825, becoming a strong supporter of Jackson . After serving as chairman of the Ways and Means Committee, he became Speaker in 1835, the only president to have been Speaker . Polk left Congress to run for governor; he won in 1839, but lost in 1841 and 1843 . He was a dark horse candidate for the Democratic nomination for president in 1844; he 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 secure the necessary two - thirds majority . In the general election, Polk defeated Henry Clay of the rival Whig Party . </P> <P> Polk is considered by many the most effective president of the pre--Civil War era, having met during his four - year term every major domestic and foreign policy goal he had set . After a negotiation fraught with risk of war, he reached a settlement with the United Kingdom over the disputed Oregon Country, the territory for the most part being divided along the 49th parallel . Polk achieved a sweeping victory in the Mexican--American War, which resulted in the cession by Mexico of nearly all the American Southwest . He secured a substantial reduction of tariff rates with the Walker tariff of 1846 . The same year, he achieved his other major goal, re-establishment of the Independent Treasury system . True to his campaign pledge to serve only one term, Polk left office in 1849 and returned to Tennessee; he died in Nashville, most likely of cholera, three months after leaving the White House . </P> <P> Scholars have ranked Polk favorably for his ability to promote and achieve the major items on his presidential agenda, but he has been criticized for leading the country into war against Mexico and for exacerbating sectional divides . A slaveholder for most of his adult life, he owned a plantation in Mississippi and bought slaves while President . A major legacy of Polk's presidency is territorial expansion, as the United States reached the Pacific coast and became poised to be a world power . </P>

Who was the u.s. president during the mexican – american war which idea did he support
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