Due to the railroads, American settlers were able to travel west in larger numbers. How did this migration impact American Indians

The expansion of the United States railroad system had a strong negative effect on the American Indians, since the increase white settlement that came along with it forced the removal of many Natives from their lands and homes, oftentimes with violence.

I believe the answer is: American Indians' way of life changed because buffalo herds were destroyed for commercial markets.

The migration make a lot of people able to settle to the territory that previously been occupied by Americna Indians. This force some of them to leave the territory or change their way of life to conform and adapt to the new way of life created by the settlers.