What are four great population movements in the history of the USA?

What are four great population movements in the history of the USA?

According to American historians and specialists in demography, that is, the study of statistics related to population, there are four great population movements in the histo​ry of the United States.
①The first was between the end of the civil war and 1880 when the westward movement came to a halt. In this period, the flow of population was from the densely-populated east coast to the sparsely-populated west.
②The second was between 1890 and 1920, a period when the United States realized its industrialization and urban​ization. The main feature was the movement of population from the rural areas to cities.
③The third was from 1920 to 1960 with the 1940s，the war years, as the peak. In this peri​od a large number of black people moved out of the south to other areas.
④The fourth and the last one so far is from the end of the 1960s till now. In this period, the population flow is from the Northeast and Central North to the West and the South, that is, to the sunbelt areas. Population in the South increased by 55.47% between 1960 and 1990 and population in the West increased by 88.17% in the same period.