Throughout the history of the nation, the United States and its citizens have never been satisfied with what they have. During the mid-nineteenth century, this was especially the case. The idea of Manifest Destiny, the idea that America was destined - by God and by history - to expand its boundaries over a vast area, led to the spread of slavery over vast new lands, and a bitter feud between the North and the South over this issue. The increased tensions induced by the expansion of slavery to new lands is what caused the "United" States of America to break into the American Civil War.

Although many Americans saw the Mexican lands as a virus, eating away at our bonds as Americans, President James K. Polk didn't see it that way. He felt that through annexing Texas, they would be promoting peace and actually diminishing their chances of...