Which of the following are true about railroad expansion in the 19th century choose all that apply
1. Railroads played a critical role in the westward expansion of the United States.
2. The construction of railroads often involved the exploitation of immigrant labor.
3. The federal government provided significant financial assistance to railroad companies through land grants and subsidies.
4. Railroad expansion contributed to economic growth and industrialization in the United States.
5. The construction of railroads led to conflicts with Native American tribes over land rights and resources.