To what extent did 'Manifest Destiny' play an important role in American westward expansion?

The theory of ‘Manifest Destiny’ did not necessarily play a significant role in aggressive American expansion; instead, it acted as an appropriate guise for the justification of American desires to occupy the continent. It would be an oversimplification to base the founding of three separate major American territories (Texas, Oregon and California) on an American belief in the preordained will of God, and their own moral and civil superiority. Of course, the belief in superiority was a contributing factor that engaged public opinion in efforts to settle, but it was more down to other, more important factors. These can be categorised as economic, religious and defensive; however, it is predominantly the economic reasons that inspired American expansionism. Underlying the religious missions in Oregon, the defensive strategy to protect pioneers in Texas, and the aggressive war with Mexico, was a need from America to lift itself from economic depression. Expansionism was the most obvious solution, as it enabled a greater control of continental trade and commerce, and gave the American government more resources to foster the wealth and power of their country. In this regard, it was not so much the theory of ‘Manifest Destiny’, but was instead a tangible need for economic progression that inspired aggressive American expansion in the 19^th century.