In the 1860s less than 8% of the African-American population lived in the Northeast or Midwest. Even by end of the 19th century, roughly 90% of all African-Americans still lived in the South. In the 20th century, huge numbers of African-Americans left the South to escape sharecropping, worsening economic conditions, and the Klu Klux Klan.
The migration of African Americans out of the South has few parallels in U.S. history.
In terms of magnitude only the migration west following the discovery of gold in California comes to mind; in terms of notoriety, only the Dust Bowl migration out of the mid west in the 1930s.
Plot the migrations of African Americans within the U.S. since 1965