Worth, during the Mexican-American War.1855. Library of Congress. In 1844, President James K. Polk ran on a Democratic platform that supported manifest destiny, the idea that Americans were ...

Worth, during the Mexican-American War.1855. Library of Congress. In 1844, President James K. Polk ran on a Democratic platform that supported manifest destiny, the idea that Americans were ...

Behind her, the president turned to a historical map of territory controlled by Mexico before the 19th century Mexican-American War that are now part of the U.S.. The territory ceded in the Treaty ...