James K. Polk and the Expansionist Impulse

In James K. Polk and the Expansionist Impulse, author Sam Haynes explores Polk's passion for the expansionist approach to increase U.S. territory. Polk wanted to incorporate California and New Mexico into United States territory and was not hesitant about boldly pursuing that goal. The timing of his presidency in terms of achieving it was optimum. Shortly before he took office, the concept of Manifest Destiny was developed by journalist John Louis O'Sullivan, and it became a catchphrase for expansionism.

O'Sullivan believed that it was America's God-given destiny to expand and possess the entire North American continent, and that this expansionism superseded any laws that would hinder it, answering instead to a higher authority God. When a border dispute subsequently occurred between the United States and Mexico, Polk parlayed it into an opportunity to position the United States against the smaller and less equipped Mexico, entering into the Mexican-American War. This war occupied much of Polk's presidency, and revealed a great deal about his personality and character especially his activism with regard to expansion and his shrewd diplomacy.

There were a number of factors that were brewing between the United States and Mexico at the time. American expansionist policies were treading on sensitive toes in other nations, particularly Mexico, and President Polk's political personality was also seen as somewhat abrasive. The annexa