James Knox Polk (November 2, 1795 - June 15, 1849) was the 11th President of the United States (1845-1849).Polk served as the 17th Speaker of the House of Representatives (1835-1839) and Governor of Tennessee (1839-1841). Polk was the surprise (dark horse) candidate for president in 1844, defeating Henry Clay of the rival Whig Party by promising to invade and annex Texas.