The common factor in US migration patterns in the middle decades of the 20th century was rural depopulation, with over half of the nation’s 3,100 counties registering absolute declines in population. Choice of urban destination was more mixed. The ‘Great Migration’ of African Americans from the southern states resumed in the war years, pulled by the boom in munitions industries. Its primary termini were still the northeastern cities, but the West was also magnetic, more than tripling the African American proportion of its population (1940–60). The Midwestern rural exodus initiated by the long agricultural Depression (1921–40) was sustained from World War II on by rapid mechanization and increase in farm size. The destinations of choice for these overwhelmingly white migrants were the western ‘Sunbelt’ states. Florida was immune from the southern exodus because of the development of air-conditioning and concentration of wartime airbases (plus multiplier industries) and from 1949, the space industry.
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