The rapid mobilization of resources and weapons during World War II prompted many African Americans to migrate to Northern and Western cities in search of jobs in the booming munitions industry. ( world war II)
The Great Migration was the relocation of more than 6 million African Americans from the rural South to the cities of the North, Midwest and West from about 1916 to 1970. ( world war I)
Explanation:
A date was not specified but i hope this is what you meant!
There was abundant rainfall and seasonal flooding within the landscape the the Olmec Civilization resided in. They also practiced slash and burn crop planting in addition to planting along the river banks.