Gone With The Wind

There was a land of Cavaliers and Cotton Fields called the Old South. Here in this pretty world, Gallantry took its last bow. Here was the last ever to be seen of Knights and their Ladies Fair, of Master and of Slave. Look for it only in books, for it is no more than a dream remembered, a Civilization gone with the wind…

Is the above in Margaret Mitchell’s book “Gone with the Wind” or is this a quote by someone else—

Sidney Howard — http://publicquotes.com/quote/28783/there-was-a-land-of-cavaliers-and-cotton-fields-called-the-old-south.html

David O. Selznick —http://www.webmousepublications.com/itow/comment/com-oldsouth.html

Ben Hecht —- http://www.goodreads.com/quotes/show/337085

I found these 3 and got tired of looking. Does anyone know?