The event that marked the beginning of the Great Migration was the migration of African Americans from the rural South to urban areas in the North during the early 20th century, particularly during and after World War I. Factors such as economic opportunities in northern industries, the promise of better living conditions, and the pervasive racism and violence in the South drove this massive demographic shift. The Great Migration saw millions of African Americans seeking to escape oppressive Jim Crow laws while pursuing jobs in factories and other sectors. This migration profoundly transformed urban landscapes and contributed to the cultural vitality of African American communities in cities like Chicago, Detroit, and New York.