Name a country where internal migration has occurred explain the reasons for this migration

The United States saw a massive internal migration from the eastern states toward the west coast during the mid-19th century, a similar large-scale migration of African Americans from the agricultural south to the industrialized northeast in the early to mid-twentieth century and a large-scale reverse migration of African Americans from other parts of the country to the urban south beginning in the late 20th century and continuing to the present.