I think the idea that the two genres grew up in the same neighborhoods needs a little more fleshing out, because its exactly true.

In the 20s and 30s, rural southerners moved to the cities in droves to get away from the dperessed southern agrarian economy and to find jobs in the newly industrialized cities. When they got to the big cities, they may have changed location, but they were still poor as dirt and often lived in the slums right next to the segregated blacks. Radio was very young and had not replaced the home musicians for entertainment, so musical tradition ran very strong in these two groups, and the close contact jsut influenced each other. (an aside: I think that the same phenomenon could be slightly responsible for the current boom in rap/heavy metal hybrids in mainsteam music. Those are the two most prevalent genres I heard in the Married Student Housing slum I lived in last year.)

Jimmie Rodgers, A.|P. Carter, Hank Williams, and Bill Monroe all were said to have studied closely with blues musicians.