1939- (National Culture) From Parting the Waters by Taylor Branch p54 :

Hollywood marked the attainment of full maturity the same way it had marked its birth a quarter century earlier with a milestone film touching the subject of race and the Civil War. Like The Birth of a Nation, Gone With the Wind contributed heavily to a national consensus that for sixty years had been building on a foundation of nationalism, Social Darwinism, and psychological avoidance. The result was that no remotely accurate history of post Reconstruction race relations survived in the majority culture, even in advanced scholarship. Gone were the odysseys of Spelman and dozens of schools like it, along with the stories of hundreds of lesser schools, thousands of missionary educators, and scores of Negro statesmen whose forbearance was recorded in unknown speeches of florid Victorian eloquence. Gone also was unbecoming realism about the reestablishment of legal white supremacy . The national consensus became so strong that the very subject of race was reduced to distorted subliminal images as captured in the two films and sophisticated white Americans took it for granted that the Civil War sprang from causes that had little if anything to do with race. After uncomfortable reality was bleached from recognized history, what remained, ironically, was the very thing the new film claimed was gone with the wind- the romance.