Final answer:
The westward expansion was influenced by demographic growth, declining eastern soil fertility, political motives related to British threat perceptions and Jeffersonian ideals, economic ambitions for trade and resource exploitation, and the cultural concept of Manifest Destiny. Federal policies and military actions enabled the acquisition and settlement of land, often at the expense of Indigenous peoples. The expansion led to significant cultural and economic changes and mixed effects on various societal groups.
Step-by-step explanation:
The westward expansion in the United States during the 19th century was driven by a mix of various demographic, economic, and political factors. The population growth from five million to over twenty million between 1800 and 1850 increased the demand for land, as did declining soil fertility in eastern farms. Political motives stemmed from fears of British occupation if the U.S. failed to claim the West and a desire to continue developing a society based on Jefferson's yeoman farmer ideal. Additionally, the concept of Manifest Destiny suggested a moral imperative to spread American ideals and control. Economic incentives included the need for new trading ports on the west coast for commerce with Asia, facilitated further by the discovery of gold in California and the development of infrastructure like railroads. The federal policies and military actions during this time played significant roles in the expansion by removing Native American populations and promoting settlement.
Cultural forces also played a part, as the belief in American superiority and civilizing missions justified the expansion in many settlers' eyes. However, this led to severe conflict and left lasting impacts on Indigenous cultures. The transition from individual to corporate opportunities in the mining and cattle industries highlighted the change from small-scale endeavors to large, profitable businesses that shaped the future of the American West.
The expansion not only changed the landscape and demographics of the nation but also provided and limited opportunities for women and African Americans, altered foreign relations, and had a lasting effect on the culture and economy of the United States.