In assuring the strength (economic and geographic) of the United States, there was no more significant war than that fought with Mexico in 1846-48. The Mexican War provided the country not only with a significant amount of land, but it provided the country with a significant amount of natural recourses on that land.

Along with assuring the United States rights to Texas, another major goal of James K. Polk heading into the Mexican War was to obtain California. Not only did the Unites States obtain California and Texas through the treaty of Guadalupe Hidalgo, but they obtained the land that is the present day states of Utah, Nevada, and parts of Arizona, New Mexico, Colorado and Wyoming as well. In total the Mexican Cession, including Texas, increased the size of the United States by one third, a total even larger then that of the Louisiana Purchase. Before the...