Library of Congress
Loc: America's Story: James K. Polk
James K. Polk was the "dark horse" candidate in the presidential election. To learn more about this president, the Library of Congress has a site complete with actual cartoons of the time.
Smithsonian Institution
National Museum of American History: American Presidency: James K. Polk
Brief biographical sketch of America's eleventh president includes background information on the era in which he served and linked-to objects from the Smithsonian's collections that help define the man and his presidency.