Why did American settlers continue to push westward during the second half of the 19th century?

American settlers continued to push westward during the second half of the 19th century due to a combination of factors, including the belief in Manifest Destiny, which held that it was America's destiny to expand across the continent. Economic opportunities, such as the promise of fertile land, mining prospects, and the potential for new markets, also motivated migration. Additionally, advancements in transportation, such as the railroad, made travel to the West more accessible and appealing. This westward expansion was often accompanied by the displacement of Indigenous peoples and significant environmental changes.