James Knox Polk was the 11th President of the United States . Polk was born in Mecklenburg County, North Carolina. He later lived in and represented Tennessee. A Democrat, Polk served as the 17th Speaker of the House of Representatives and Governor of Tennessee . Polk was the surprise candidate for president in 1844, defeating Henry Clay of the rival Whig Party by promising to invade and annex Texas. Polk was a leader of Jacksonian Democracy during the Second Party System.