How was massive migration an integral part of Western expansion?

Massive migration was integral to Western expansion as it facilitated the settlement and development of vast territories in the United States. The influx of settlers, driven by the promise of land and opportunity, led to the establishment of new communities and economies. This movement also intensified conflicts with Indigenous populations and spurred the construction of transportation networks, which further connected the East and West. Ultimately, the migration reinforced the ideology of Manifest Destiny, promoting the belief that Americans were destined to expand across the continent.