Long before the Civil War, the southern states had realized the importance of state sovereignty. The infringement upon the rights of state sovereignty was a perpetual source of discontent and animosity between the North and. South. John O. Calhoun, the proponent of states' rights, clearly stated his views in the doctrine of nullification. He argued that since the Union is the creation of states and not the states of the Union it stands to reason that the former will be subordinate to the latter in case there is a dispute as to respective powers; for the creator is alwavs greater than the creature. The South was anxious to have an alliance with the West and to win over that section to its own political views. Such a union would insure the southern planters and the western farmers against objectionable measures advocated by northern manufacturers and would give them a controlling voice in the Federal government. The key to the southern expansionist problem was to be found in Mexico. Mexico was to be the lever by which the South could attain its goal.