The Great Migration Creates the Black Metropolis
Beginning during World War I, the Great Migration more than sextupled Chicago’s African American population to nearly 280,000 by 1940, creating what sociologists St. Clair Drake and Horace Cayton immortalized as the “Black Metropolis.” The next wave of migration that began during World War II dwarfed the first, nearly quadrupling the city’s black population to more than 1.1 million by 1970. Chicago was just one of many cities in the North and West transformed by these migratory patterns. In what historian James Gregory has called “a turning point in the long struggle for rights and respect” by African Americans, nearly eight million black Southerners migrated to points North and West; by 1970, 47% of African Americans lived outside of the South. 
The influx of migrants following World War II and the already acute deficit of adequate housing in the segregated Black Belt combined to create a critical situation on Chicago's South Side and, to a lesser extent, the West Side. Richard Wright observed in 1951, "The South Side apartment buildings were jammed to bursting with Negroes from Mississippi, Texas, Louisiana, Arkansas, Tennessee, and points South. The South Side was still a Black Belt, but it had swollen and burst its banks," remaining "an undissolved lump in the city's melting pot.” 
As two historians would later put it, “In this vast black metropolis, African Americans lived apart in their own self-defined world that resembled the Mississippi Delta as much as Chicago. On the South Side, African Americans found themselves geographically confined, economically and politically limited, socially excluded, and racially feared. Their growing numbers fed white racial hostility that led to conflicts over housing, neighborhoods, and jobs.”  Wright similarly contended that, "Chicago whites still grudgingly withhold from the Negro the right to living space, full citizenship, job opportunities; but the Negro, within these hopeless limits, is making progress in his material standards of living, in education, in business, in culture and in health.” 
One mark of that cultural progress was the Chicago Defender’s annual Bud Billiken Day parade and picnic. Begun in 1930 in part as a response to the Great Depression, the youth-focused event had become a treasured community institution by the time the Black Belt grew by leaps and bounds after World War II, hosting such black luminaries as Joe Louis, Duke Ellington, Muhammad Ali, and James Brown as well as former President Harry Truman. 
When Raeburn Flerlage photographed Bud Billiken Day festivities in the 1960s (see images at left, and click for more information), he captured crowds on rooftops and a rapidly changing community uniting for an annual late summer celebration even as it fought against the restrictions imposed upon it. See the Mapping the Blues interactive map for even more images that situate the annual Billiken Day parade and picnic within the South Side's built environment and blues culture.
 James N. Gregory, The Southern Diaspora: How the Great Migrations of Black and White Southerners Transformed America, (Chapel Hill: University of North Carolina Press, 2005), 113, 14, 18.
 Richard Wright, "The Shame of Chicago," Ebony 7.2 (December 1951), 28.
 Peter M. Rutkoff and William B. Scott, Fly Away: The Great African American Cultural Migrations, (Baltimore: The Johns Hopkins University Press, 2010), 206.
 Wright, "The Shame of Chicago," 32.
 Rutkoff and Scott, Fly Away, 222-231.