Answer:
The Great Migration.
Step-by-step explanation:
The historical event that gave birth to the Rock and Roll music genre was the Great Migration. The Great Migration of the twentieth century in the United States took place when millions of African Americans (former black slaves) migrated from the South to the Northwest, West and Midwest in search of better living.
This migration, for the first time in the history of the US, enabled Blacks and Whites living in proximity. This close proximity enabled them to listen to each other's music which gave birth to the 'Rock and Roll' music genre. The music is derived from rhytms and blues music.
Therefore, the correct answer is the Great Migration.