Tens of thousands of African Americans left Mississippi by train, foot, or boat to migrate north starting in the 1880s; migration reached its pinnacle during and after World War I. In the Great Migration, they went North to leave the violence and a society that had closed off opportunity. Another wave of migration arose in the 1940s and 1950s. Almost half a million people, three-quarters of them black, left Mississippi in the second migration, many seeking jobs in the burgeoning wartime defense industry on the West Coast, particularly in California.