In her new book, Caste: The Origins of Our Discontents, Wilkerson says that acknowledging America's caste system deepens our understanding of what Black people are up against in the U.S.
More than 6 million African-Americans moved from the South to cities in the Northeast and Midwest between 1915 and 1970. Pulitzer Prize-winning journalist Isabel Wilkerson documents the resulting demographic and social changes in her history of the Great Migration, The Warmth of Other Suns.