Between roughly 1910 and 1970, approximately six million Black Americans relocated from the rural South to cities in the North, Midwest, and West in two waves — the first from 1910 to 1940, the second from 1940 to 1970. Driven by the violence and economic oppression of Jim Crow, the promise of industrial employment, and the labor demands of two World Wars, the migration fundamentally transformed American cities, politics, and culture. It created the conditions for the Harlem Renaissance, the Chicago blues tradition, and the urban civil rights movement.