The primary cause of the Great Migration of African Americans in the early 20th century was the search for better economic opportunities and escape from racial discrimination in the South. Following World War I, many African Americans moved in significant numbers to northern cities like Chicago and New York, driven by the availability of industrial jobs and the promise of a more equitable society. This migration profoundly transformed American urban demographics, culture, and contributed to the Harlem Renaissance, highlighting the quest for civil rights and social justice.