I learned all of this from Thomas Sowell's Discrimination and Disparities, it's a great book that pretty annihilates every leftist talking point with things like the gender pay gap, black failure, or the ridiculous notion that America is tailor made for whites when Asians exist. The migration of Southern Blacks to the North is called The Great Migration, that lasted from 1916 to 1970. Here's the book in question with the chapter that talks all about this. https://youtu.be/ihb4ny4wKXQ?t=7125