The Great Migration created the first large, urban black communities in the North. The North saw its black population rise about 20 percent between 1910 and 1930. Cities such as Chicago, Detroit, New York, and Cleveland saw some of the biggest increases.
World War I and boll weevils were major factors in pulling blacks to the North. The war created a huge demand for labor in the North when it caused millions of men to leave their jobs to serve in the armed forces and forced immigration to slow down. In the South, a boll weevil infestation of the cotton crop that ruined harvests and threatened thousands of African Americans with starvation also caused people to head North.
Railroad companies were so desperate for help that they paid African Americans' travel expenses to the North. While northern labor agents traveled to the South to encourage blacks to leave and go find jobs in the North.
With black labor leaving the South in large numbers, southern planters tried to prevent the outflow, but were ultimately unsuccessful. The more progressive southern employers tried to promise better pay and improved treatment. Others tried to intimidate blacks, even going so far as to board northbound trains and to attack black men and women to try to force them into returning to the South.
Despite the jobs and housing available in the North, the challenges of living in an urban environment were daunting for many of the new migrants.
The stream of migrants continued apace, however, until the Great Depression and World War II caused northern demand for workers to slacken.