How have population changes raised issues for americans as they entered the 21st century?

The "nationalists" and fascists battled against the "republicans" and communists in a civil war in the 1930s in

The factory system of the early-19th century caused a) a decrease in farm production. b) an increase in rural population. c) an increase in urban population. d) high unemployment in other areas.

In what is known as the great migration, large numbers of african americans moved from the rural south to northern cities, beginning in the early twentieth century. what motivated this large-scale movement?