Final answer:
The term for southern blacks moving to urban centers in the North and Midwest during WWI is 'The Great Migration.' This involved around 1.5 million African Americans between 1910 and 1930.
Step-by-step explanation:
The term applied to southern blacks relocating to urban centers in the North and Midwest during World War I is The Great Migration. This movement involved approximately 1.5 million African Americans leaving the American South between 1910 and 1930, with about half a million migrating during the war itself, taking advantage of wartime employment opportunities in Northern factories.
The Great Migration was a major demographic shift that saw African Americans moving to cities like New York, Chicago, Philadelphia, and Detroit to escape Jim Crow laws and seek better economic conditions.