Westward expansion refers to the movement of settlers into the West of America around the nineteenth century. (From what I remember), it began with the Louisiana Purchase (basically the purchase of the state of Louisiana) and was intensified by the Gold Rush, the Oregon Trail as well as a belief in Manifest Destiny.
In conclusion, Westward expansion provided the United States with many natural resources and ports along the Atlantic, Pacific and Gulf coasts which allowed the expansion of trade. They also play key elements in creating the strength of America today.
