The worst race riot in American history occurred in 1921, when more than 300 blacks were killed and over 10,000 were left homeless after white mobs burned an all-black section of which city to the ground?

Tulsa, Oklahoma

Explanation:

Tulsa Race Massacre of 1921 witnessed as one of the worst racial riots in the history of the United States where a white mob set fire to the black business district in which more than 300 blacks were killed and over 10,000 were left homeless. What started from the news of black teenager sexual assault on a white woman has engulfed the city of Tulsa where the city officials were even reported to provide weapons to the violent mob.