By 1960 more than 50 percent of African Americans lived in the South.
African Americans did not begin leaving the south in large numbers until the second decade of the twentieth century, when ww1 (1914-18) provided a critical new "pull" factor that greatly accelerated the migration of African Americans to northern cities.
http://school.eb.com/levels/middle/article/603604
HODGE, CHELSEA. "Ain't Got No Home: America's Great Migrations And The Making Of An Interracial Left." Arkansas Historical Quarterly 73.4 (2014): 457-459. History Reference Center. Web. 30 Mar. 2016.
"Great Migration, 1910–70." Gale Encyclopedia of U.S. Economic History. Ed. Thomas Riggs. 2nd ed. Vol. 2. Farmington Hills, MI: Gale, 2015. 530-533. Biography in Context. Web. 30 Mar. 2016.
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