reword this into making it sound like a semi-formal high school student. "In the economic realm, the 1840s witnessed a surge in industrialization in the eastern United States, leading to increased demand for raw materials and new markets for manufactured goods. This economic growth spurred a desire for expansion into untapped territories where these resources could be found. Moreover, the idea of the "frontier thesis," popularized by historian Frederick Jackson Turner in the late 19th century, argued that the existence of a continuously advancing frontier was essential for American democracy and individualism. Thus, the economic impetus for expansion remained consistent, driven by the quest for resources, markets, and the belief in the transformative power of westward expansion on American society. Socially, the period surrounding the 1840s saw the continuation of deeply ingrained racial and cultural prejudices that justified the subjugation and displacement of indigenous peoples. The ideology of Manifest Destiny often served as a rationale for the forced removal of Native American tribes from their ancestral lands, epitomized by the Trail of Tears in the 1830s. Similarly, the annexation of Texas and the Mexican-American War (1846-1848) led to the acquisition of vast territories inhabited by Mexican and indigenous populations, raising questions of citizenship, land ownership, and cultural assimilation. In the realm of foreign policy, the period before the 1840s was characterized by a cautious approach to territorial expansion, with efforts focused on consolidating control over existing territories rather than aggressively acquiring new ones. However, the 1840s marked a shift towards a more assertive expansionist agenda, epitomized by President James K. Polk's campaign promise to annex both Texas and Oregon. The resolution of the Oregon boundary dispute through negotiation with Britain and the subsequent annexation of Texas reflected a newfound confidence in American territorial ambitions and set the stage for further expansion into the Southwest and the Pacific. In conclusion, the motivation and rationale behind Manifest Destiny expansion in the 1840s were multifaceted, driven by economic interests, ideological beliefs, and geopolitical ambitions. While certain aspects of expansion remained consistent, such as the quest for economic opportunities and the assertion of American exceptionalism, the period surrounding the 1840s witnessed significant changes in terms of the pace and scope of westward expansion, as well as the methods used to justify and pursue territorial acquisition."