Which of the following are true about railroad expansion in the late 19th century? Select the three correct answers.
1) Railroad expansion was primarily concentrated in the southern states.
2) The transcontinental railroad was completed in 1861.
3) The federal government provided substantial financial support to the railroad industry.
4) Railroad construction was fully driven by private investment and no government involvement.
5) Railroad expansion led to the creation of national time zones.
6) The construction of railroads led to a decrease in the cost of transportation.
7) Railroad expansion resulted in the displacement and mistreatment of Native American tribes.