The Great Migration had significant effects on American urban development, particularly between the early 20th century and 1970. As millions of African Americans relocated from the rural South to northern and western cities seeking better economic opportunities and escaping racial oppression, urban areas like Chicago, Detroit, and New York experienced rapid demographic shifts. This influx led to the growth of vibrant black communities and cultural movements, including the Harlem Renaissance. However, it also resulted in challenges such as housing discrimination, racial tensions, and increased segregation, which shaped social dynamics in U.S. cities for generations.