James Knox Polk - Biography. 11th president of the United States Birth November 2, 1795 Death June 15, 1849 Home State Tennessee Party Democrat Term In Office 1845-1849 Vice President George Mifflin Dallas Significant Lowered the tariff on imported goods by signing the Walker Tariff in 1846. Acts Added the Oregon Territory to the United States in 1846 by skillful negotiation with Britain. Commanded the United States in the Mexican War (1846-1848), which ended in a U.S. victory and significant territorial gains for the United States. Career 1823-1825 Served in the Tennessee House of Representatives. 1825-1839 Represented Tennessee in the U.S. House of Representatives. 1835-1839 Served as speaker of the House. 1839-1841 Served as governor of Tennessee. 1845-1849 President of the United States. Did You Know Polk laid the cornerstone of the Washington Monument in Washington, D.C., on July 4, 1848. Sedated only by brandy, Polk survived gall bladder surgery at the age of 17. The announcement of Polk's nomination for president via telegraph was the first use of this technology in politics. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.