was the 11th President of the United States (1845-1849). A Democrat, served as the 17th Speaker of the House of Representatives (1835-1839) and the 12th Governor of Tennessee (1839-1841). was the surprise ("dark horse") candidate for president in 1844, defeating Henry Clay of the rival Whig Party by promising to annex Texas. was a leader of Jacksonian Democracy during the Second Party System. was the last strong pre-Civil War president, and he is the earliest of whom there are surviving photographs taken during a term in office. He is noted for his foreign policy successes. He threatened war with Britain over the issue of which nation owned the Oregon Territory, then backed away and split the ownership of the region with Britain. When Mexico rejected American annexation of Texas, he led the nation to a sweeping victory in the Mexican-American War, which gave the United States most of its present Southwest. He secured passage of the Walker tariff of 1846, which had low rates that pleased his native South, and he established a treasury system. he oversaw the opening of the U.S. Naval Academy and the Smithsonian Institution, the groundbreaking for the Washington Monument, and the issuance of the first postage stamps in the United States.