Final answer:
Western settlement expanded to include a diverse population due to economic opportunities, land availability, and political pressures, alongside the arrival of European immigrants, African Americans, Hispanics, and Chinese. These new settlers often faced discrimination and conflict but contributed significantly to the development and multiculturalism of the American West.
Step-by-step explanation:
The western settlement of the United States expanded from mainly white easterners to a more diverse population due to several contributing factors. Initially, many White Americans of means ventured west seeking opportunities in gold, cattle, or farming, or to spread Protestant ideals. They were soon followed by European immigrants, especially from Northern Europe, and African Americans escaping the South's racism, creating a mix of cultures and traditions.
However, these settlers also encountered and often came into conflict with Native American tribes, Hispanic Americans who'd been in the Southwest since the end of the Mexican-American War, and Chinese immigrants. The latter arrived in significant numbers during the California Gold Rush. Despite being citizens with rights, these groups often found themselves marginalized and discriminated against, retreating into homogeneous communities where their languages and cultures could survive.
Demographic growth, economic incentives, and political pressures further contributed to the diversity of western expansion. The population explosion in the U.S. led to a land-hungry nation, seeking new territories for agriculture and political influence, often at the expense of existing populations like Mexican nationals in Texas and Native Americans. Immigrants and Americans alike saw the west as a means to improve their socio-economic positions, contributing to the diversification of the settlers and to the U.S.'s emerging multicultural society.