Amos H. Hawley Sarah Mills Mazie
In the years since 1920, extending up to 1970, three distinguishable though interwoven trends of population distribution were in process. Each differed in respect to its duration and its territorial scope. The oldest and broadest of these was a continuation of the interregional movement of population toward the West. That drift, due partly to differential natural increase and partly to a net westward migration, is represented by the continued relocation of the center of continental population as plotted by the U.S. Bureau of the Census ( 1972). Noteworthy is the fact that the line of movement has been toward the southwest since 1910. The southern turn of the westward drift became more pronounced after 1960 as the southeast began to exercise a new pull on the course of redistribution.
A second trend, also with a history beginning in the preceding century, has operated within regions. That is the familiar rural to urban, and more recently the nonmetropolitan to metropolitan, movement of population. The rapid mechanization of agriculture combined with the decline of foreign immigration after the 1920s accelerated the urbanward migration of the domestic population. In the fifty years ending in 1970 the urban share of the total population increased from 51 percent to 73 percent. During that five-decade period the rural population changed very slightly in absolute number, from 51 million to 54 million. The composition of the rural population, however, shifted dramatically; the farm population declined from 30 percent of the total to less than 5 percent, while the rural nonfarm proportion increased from 19 to 22 percent. That shift may be regarded as a harbinger of events to come. Most of the urban population and a substantial share of the rural population was being absorbed in metropolitan areas that were growing in number and geographical scope as well as in proportion to the total population. Of the counties