James K. 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 Jacksonian democracy and extending the territory of the United States. Polk led the U.S. into the Mexican–American War, and after winning the war he annexed the Republic of Texas, the Oregon Territory, and the Mexican Cession.

Source: Wikipedia